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<div id="header">
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<h1 class="title">Strudel: live coding patterns on the Web</h1>
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<ul id="authorlist">
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<li>true</li>
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<li>true</li>
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</ul>
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<h3 class="date">2022-12-14</h3>
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</div>
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<h2 class="abstract">Abstract</h2>
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<div id="abstract">
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<p>
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This paper introduces Strudel, which brings the TidalCycles approach to live coding algorithmic patterns to
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native JavaScript and the web. We begin by giving a little background of the first year of development, before
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sharing some detail about its implementation and examples of use. We go on to outline the wide range of
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synthesis and other outputs available in Strudel, including WebAudio, MIDI, OSC (for SuperDirt), WebSerial and
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CSound, and introduce Strudel’s REPL live editor, including its built-in visualisations. We then compare Strudel
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with Tidal, the trade-offs involved between JavaScript and Haskell, and the unique capabilities offered by
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Strudel for aligning patterns.
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</p>
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</div>
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<h1 data-number="1" id="introduction"><span class="header-section-number">1</span> Introduction</h1>
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<p>
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In the following paper, we introduce <em>Strudel</em>, an alternative implementation of the TidalCycles (or
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‘Tidal’ for short) live coding system, using the JavaScript programming language. Strudel is an attempt to make
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live coding more accessible, by creating a system that runs entirely in the browser, while opening Tidal’s
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approach to algorithmic patterns
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<span class="citation" data-cites="mcleanAlgorithmicPattern2020a">(Mclean 2020)</span> up to modern audio/visual
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web technologies. The Strudel REPL is a live code editor dedicated to manipulating patterns while they play, with
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builtin visual feedback. While Strudel is written in JavaScript, the API is optimized for simplicity and
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readability by applying code transformations on the syntax tree level, allowing language operations that would
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otherwise be impossible. The application supports multiple ways to output sound, including Tone.js, Web Audio
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Nodes, OSC (Open Sound Control) messages, Web Serial, Web MIDI and Csound. The project is split into multiple
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packages, allowing granular reuse in other applications. Apart from TidalCycles, Strudel draws inspiration from
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many prior existing projects like TidalVortex
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<span class="citation" data-cites="mcleanTidalVortexZero2022">(McLean et al. 2022)</span>, Gibber
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<span class="citation" data-cites="robertsGibberLiveCoding2012">(Roberts and Kuchera-morin 2012)</span>, Estuary
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<span class="citation" data-cites="ogbornEstuaryBrowserbasedCollaborative2017">(Ogborn et al. 2017)</span>, Hydra
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<span class="citation" data-cites="jackHydra2022">(Jack [2022] 2022)</span>, Ocarina
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<span class="citation" data-cites="solomonPurescriptocarina2022">(Solomon [2021] 2022)</span> and Feedforward
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<span class="citation" data-cites="mcleanFeedforward2020">(McLean 2020)</span>. This paper expands the Strudel
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Demo paper for the Web Audio Conference 2022
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<span class="citation" data-cites="StrudelWAC2022">(Roos and McLean 2022)</span>.
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</p>
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<p>
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The first tentative commit to the Strudel project was on 22nd January 2022 by Alex McLean, with the core
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representation implemented over the following few days. Although this was his first attempt at a JavaScript-based
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application, by 27th January, Alex had managed to upload the initial version to the ‘npm’ javascript package
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database, sharing with the wider community for comment. By 4th February, Felix Roos had discovered Strudel and
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contributed a ‘REPL’ user interface to it, and then contributed a scheduler the next day, so that Strudel could
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already make sound. At this point, Alex and Felix shared ownership to the repository, and the project has since
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proved to be a productive confluence of Felix’s own work into music representation and visualisation, with Alex’s
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experience with making Tidal. Felix has since become the primary contributor to Strudel, with Alex continuing to
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jump between developing both Strudel and Tidal. Aspects of Strudel’s development have therefore fed back into
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TidalCycles, and both systems have maintained a shared conceptual underpinning. We plan to continue working
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towards feature parity between these systems, although within the syntactical trade-offs and library ecosystems of
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JavaScript and Haskell, some divergence is inevitable and healthy.
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</p>
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<p>
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Over the first year of its life, Strudel is now a fully-fledged live coding environment, porting Tidal’s core
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represention of patterns, pattern transformations, and mininotation for polymetric sequences, combined with a
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wealth of features for synthesising and visualising those patterns.
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</p>
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<h1 data-number="2" id="from-tidal-to-strudel-and-back">
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<span class="header-section-number">2</span> From Tidal to Strudel and back
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</h1>
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<p>
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As mentioned above, the original Tidal is implemented as a domain specific language (DSL) embedded in the Haskell
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pure functional programming language, and takes advantage of Haskell’s terse syntax and advanced, ‘strong’ type
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system. JavaScript on the other hand, is a multi-paradigm programming language, with a dynamic type system.
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Because Tidal leans heavily on many of Haskell’s more unique features, it was not always clear that it could
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meaningfully be ported to a multi-paradigm scripting language. However, this possibility was already demonstrated
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with an earlier port to Python [TidalVortex;
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<span class="citation" data-cites="mcleanTidalVortexZero2022">McLean et al. (2022)</span>], and we have now
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successfully implemented Tidal’s pure functional representation of patterns in Strudel, including partial
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application, currying, and the functor, applicative and monadic structures that underlie Tidal’s expressive
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pattern transformations. The result is a terse and highly composable system, where everything is either a pattern,
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or a function for combining and manipulating patterns, offering a rich creative ground for exploration.
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</p>
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<p>
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This development process has been far from a one-way port, however. The process of porting Tidal’s concepts has
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also opened up new possibilities, some just from revisiting every design decision, and some from the particular
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affordances and constraints offered by JavaScript. This has lead to new features (and indeed bugfixes) that have
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found their way back to Tidal where appropriate, and ongoing work that we will return to in the conclusion of this
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paper.
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</p>
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<h1 data-number="3" id="representing-patterns">
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<span class="header-section-number">3</span> Representing Patterns
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</h1>
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<p>
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Patterns are the essence of Tidal. Its patterns are abstract entities that represent flows of time as functions,
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adapting a technique called pure functional reactive programming. Taking a time span as its input, a Pattern can
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output a set of events that happen within that time span. It depends on the structure of the Pattern how the
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events are located in time. From now on, this process of generating events from a time span will be called
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<strong>querying</strong>. Example:
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</p>
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<div class="sourceCode" id="cb1">
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<pre
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class="sourceCode js"
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><code class="sourceCode javascript"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="kw">const</span> pattern <span class="op">=</span> <span class="fu">sequence</span>(c3<span class="op">,</span> [e3<span class="op">,</span> g3])</span>
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<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="kw">const</span> events <span class="op">=</span> pattern<span class="op">.</span><span class="fu">queryArc</span>(<span class="dv">0</span><span class="op">,</span> <span class="dv">1</span>)</span>
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<span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="bu">console</span><span class="op">.</span><span class="fu">log</span>(events<span class="op">.</span><span class="fu">map</span>(e <span class="kw">=></span> e<span class="op">.</span><span class="fu">show</span>()))</span></code></pre>
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</div>
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<p>
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In this example, we create a pattern using the <code>sequence</code> function and <strong>query</strong> it for
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the time span from <code>0</code> to <code>1</code>. Those numbers represent units of time called
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<strong>cycles</strong>. The length of one cycle depends on the tempo, which defaults to one cycle per second. The
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resulting events are:
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</p>
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<div class="sourceCode" id="cb2">
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<pre
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class="sourceCode js"
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><code class="sourceCode javascript"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>[{ <span class="dt">value</span><span class="op">:</span> <span class="st">'c3'</span><span class="op">,</span> <span class="dt">begin</span><span class="op">:</span> <span class="dv">0</span><span class="op">,</span> <span class="dt">end</span><span class="op">:</span> <span class="dv">1</span><span class="op">/</span><span class="dv">2</span> }<span class="op">,</span></span>
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<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>{ <span class="dt">value</span><span class="op">:</span> <span class="st">'e3'</span><span class="op">,</span> <span class="dt">begin</span><span class="op">:</span> <span class="dv">1</span><span class="op">/</span><span class="dv">2</span><span class="op">,</span> <span class="dt">end</span><span class="op">:</span> <span class="dv">3</span><span class="op">/</span><span class="dv">4</span> }<span class="op">,</span></span>
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<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a>{ <span class="dt">value</span><span class="op">:</span> <span class="st">'g3'</span><span class="op">,</span> <span class="dt">begin</span><span class="op">:</span> <span class="dv">3</span><span class="op">/</span><span class="dv">4</span><span class="op">,</span> <span class="dt">end</span><span class="op">:</span> <span class="dv">1</span> }]</span></code></pre>
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</div>
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<p>
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Each event has a value, a begin time and an end time, where time is represented as a fraction. In the above case,
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the events are placed in sequential order, where c3 takes the first half, and e3 and g3 together take the second
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half. This temporal placement is the result of the <code>sequence</code> function, which divides its arguments
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equally over one cycle. If an argument is an array, the same rule applies to that part of the cycle. In the
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example, e3 and g3 are divided equally over the second half of the whole cycle.
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</p>
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<p>
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The above examples do not represent how Strudel is used in practice. In the live coding editor, the user only has
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to type in the pattern itself, the querying will be handled by the scheduler. The scheduler will repeatedly query
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the pattern for events, which are then scheduled as sound synthesis or other event triggers. Also, the above event
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data structure has been simplified for readability.
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</p>
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<figure>
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<img
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src="images/strudel-screenshot2.png"
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style="width: 60%"
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alt="Screenshot of the Strudel ‘REPL’ live coding editor, including piano-roll visualisation."
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/>
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<figcaption aria-hidden="true">
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Screenshot of the Strudel ‘REPL’ live coding editor, including piano-roll visualisation.
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</figcaption>
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</figure>
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<h1 data-number="4" id="making-patterns"><span class="header-section-number">4</span> Making Patterns</h1>
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<p>
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In practice, the end-user live coder will not deal with constructing patterns directly, but will rather build
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patterns using Strudel’s extensive combinator library to create, combine and transform patterns.
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</p>
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<p>
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The live coder will rarely use the <code>sequence</code> function as seen above, as sequencing is implicit in many
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functions. For example in the following, the <code>note</code> function constructs a pattern of notes, sequencing
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its arguments in the same manner as the previous example.
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</p>
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<div class="sourceCode" id="cb3">
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<pre
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||
class="sourceCode js"
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><code class="sourceCode javascript"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="fu">note</span>(c3<span class="op">,</span> [e3<span class="op">,</span> g3])</span></code></pre>
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</div>
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<p>
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Perhaps more often, they will use the mini-notation for even terser notation of rhythmic sequences: [^This last
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example is also valid Tidal code, albeit the parenthesis is not required in its Haskell syntax in this case. Tidal
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does not support passing sequences as lists directly to the <code>note</code> function, however.].
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</p>
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<div class="sourceCode" id="cb4">
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<pre
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class="sourceCode js"
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><code class="sourceCode javascript"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="fu">note</span>(<span class="st">"c3 [e3 g3]"</span>)</span></code></pre>
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</div>
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<p>
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Such sequences are often treated only a starting point for manipulation, where they then undergo pattern
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transformations such as repetition, symmetry, interference/combination or randomisation, potentially at multiple
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timescales. Because Strudel patterns are represented as pure functions of time rather than as data structures,
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very long and complex generative results can be represented and manipulated without having to store the resulting
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sequences in memory.
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</p>
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<h1 data-number="5" id="pattern-example"><span class="header-section-number">5</span> Pattern Example</h1>
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<p>
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The following example showcases how patterns can be utilized to create musical complexity from simple parts, using
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repetition and interference:
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</p>
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<div class="sourceCode" id="cb5">
|
||
<pre
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||
class="sourceCode js"
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||
><code class="sourceCode javascript"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a><span class="st">"<0 2 [4 6](3,4,1) 3>"</span></span>
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<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">off</span>(<span class="dv">1</span><span class="op">/</span><span class="dv">4</span><span class="op">,</span> <span class="fu">add</span>(<span class="dv">2</span>))</span>
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<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">off</span>(<span class="dv">1</span><span class="op">/</span><span class="dv">2</span><span class="op">,</span> <span class="fu">add</span>(<span class="dv">6</span>))</span>
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<span id="cb5-4"><a href="#cb5-4" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">scale</span>(<span class="st">'D minor'</span>)</span>
|
||
<span id="cb5-5"><a href="#cb5-5" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">legato</span>(<span class="op">.</span><span class="dv">25</span>)</span>
|
||
<span id="cb5-6"><a href="#cb5-6" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">note</span>()<span class="op">.</span><span class="fu">s</span>(<span class="st">"sawtooth square"</span>)</span>
|
||
<span id="cb5-7"><a href="#cb5-7" aria-hidden="true" tabindex="-1"></a><span class="op">.</span><span class="fu">delay</span>(<span class="op">.</span><span class="dv">8</span>)<span class="op">.</span><span class="fu">delaytime</span>(<span class="op">.</span><span class="dv">125</span>)</span></code></pre>
|
||
</div>
|
||
<p>
|
||
The pattern starts with a rhythm of numbers in mini notation, which are later interpreted inside the scale of D
|
||
minor. The first line could also be expressed without mini notation:
|
||
</p>
|
||
<div class="sourceCode" id="cb6">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="fu">cat</span>(<span class="dv">0</span><span class="op">,</span> <span class="dv">2</span><span class="op">,</span> [<span class="dv">4</span><span class="op">,</span> <span class="dv">6</span>]<span class="op">.</span><span class="fu">euclid</span>(<span class="dv">3</span><span class="op">,</span> <span class="dv">4</span><span class="op">,</span> <span class="dv">1</span>)<span class="op">,</span> <span class="dv">3</span>)</span></code></pre>
|
||
</div>
|
||
<p>
|
||
These numbers then undergo various pattern transformations. Here is a short description of all the functions used:
|
||
</p>
|
||
<ul>
|
||
<li><code>cat</code>: play elements sequentially, where each lasts one cycle</li>
|
||
<li><code>brackets</code>: elements inside brackets are divided equally over the time of their parent</li>
|
||
<li>
|
||
<code>.euclid(p, s, o)</code>: place p pulses evenly over s steps, with offset o
|
||
<span class="citation" data-cites="toussaintEuclideanAlgorithmGenerates2005">(Toussaint 2005)</span>
|
||
</li>
|
||
<li>
|
||
<code>.off(n, f)</code>: layers a pattern on top of itself, with the new layer offset by n cycles, and with
|
||
function f applied
|
||
</li>
|
||
<li><code>.legato(n)</code>: multiply the duration of all events in a pattern by a factor of n</li>
|
||
<li>
|
||
<code>.echo(t, n, v)</code>: copy each event t times, with n cycles in between each copy, decreasing velocity by
|
||
v
|
||
</li>
|
||
<li><code>.note()</code>: interpretes values as notes</li>
|
||
<li><code>.s(name)</code>: play back each event with the given sound</li>
|
||
<li><code>.delay(wet)</code>: add delay</li>
|
||
<li><code>.delaytime(t)</code>: set delay time</li>
|
||
</ul>
|
||
<p>Much of the above will be familiar to Tidal users.</p>
|
||
<!-- This example shows some of Strudel's unique support for chords and transposition familiar to students of Western music theory. This differs a little from Tidal's approach and thanks to the integration of the javascript library XXX (*TODO* ? or is this all your work Felix?), Strudel's support for tonal transformations such as voice leading is perhaps respects more advanced than Tidal. -->
|
||
<h1 data-number="6" id="ways-to-make-sound-and-other-events">
|
||
<span class="header-section-number">6</span> Ways to make Sound (and other events)
|
||
</h1>
|
||
<p>To generate sound, Strudel supports bindings for different outputs:</p>
|
||
<ul>
|
||
<li>Tone.js (deprecated)</li>
|
||
<li>Web Audio API</li>
|
||
<li>WebDirt, a js recreation of Tidal’s <em>Dirt</em> sample engine (deprecated)</li>
|
||
<li>OSC via osc-js, compatible with superdirt</li>
|
||
<li>Csound via the Csound WebAssembly build</li>
|
||
<li>MIDI via WebMIDI</li>
|
||
<li>Serial via WebSerial</li>
|
||
</ul>
|
||
<p>
|
||
At first, we used Tone.js as sound output, but it proved to be limited for the use case of Strudel, where each
|
||
individual event could potentially have a completely different audio graph. While the Web Audio API takes a
|
||
<em>fire-and-forget</em> approach, creating a lot of Tone.js instruments and effects causes performance issues
|
||
quickly. For that reason, we chose to search for alternatives.
|
||
</p>
|
||
<p>
|
||
Strudel’s new default output uses the Web Audio API to create a new audio graph for each event. It currently
|
||
supports basic oscillators, sample playback, various effects and an experimental support for soundfonts.
|
||
</p>
|
||
<p>
|
||
WebDirt <span class="citation" data-cites="ogbornDktr0WebDirt2022">(Ogborn [2016] 2022)</span> was created as part
|
||
of the Estuary Live Coding System
|
||
<span class="citation" data-cites="ogbornEstuaryBrowserbasedCollaborative2017">(Ogborn et al. 2017)</span>, and
|
||
proved to be a solid choice for handling samples in Strudel as well. We are however focused on working more
|
||
directly with the Web Audio API to be able to integrate new features more tightly.
|
||
</p>
|
||
<p>
|
||
Using the OSC protocol via Strudel’s provided Node.js-based OSC proxy server, it is possible to send network
|
||
messages to trigger events. This is mainly used to render sound using SuperDirt
|
||
<span class="citation" data-cites="SuperDirt2022">(<em>SuperDirt</em> [2015] 2022)</span>, which is the
|
||
well-developed Supercollider-based synthesis framework that Tidal live coders generally use as standard.
|
||
</p>
|
||
<p>
|
||
Recently, the experimental integration of Csound proved to bring a new dimension of sound design capabilities to
|
||
Strudel. Thanks to the WebAssembly distribution of this classic system
|
||
<span class="citation" data-cites="CsoundWebAssembly">(Yi, Lazzarini, and Costello 2018)</span>, Csound
|
||
‘orchestra’ synthesisers can be embedded in and then patterned with Strudel code.
|
||
</p>
|
||
<p>
|
||
MIDI output can also be used to send MIDI messages to either external instruments or to other programs on the same
|
||
device. Unlike OSC, Strudel is able to send MIDI directly without requiring additional proxy software, but only
|
||
from web browsers that support it (at the time of writing, this means Chromium-based browsers).
|
||
</p>
|
||
<p>
|
||
Finally, Strudel supports Serial output, for example to trigger events via microcontrollers. This has already been
|
||
explored for robot choreography by Kate Sicchio and Alex McLean, via a performance presented at the International
|
||
Conference on Live Interfaces 2022.
|
||
</p>
|
||
<h1 data-number="7" id="the-strudel-repl"><span class="header-section-number">7</span> The Strudel REPL</h1>
|
||
<p>
|
||
While Strudel can be used as a library in any JavaScript codebase, its main, reference user interface is the
|
||
Strudel REPL[^REPL stands for read, evaluate, print/play, loop. It is friendly jargon for an interactive
|
||
programming interface from computing heritage, usually for a commandline interface but also applied to live coding
|
||
editors.], which is a browser-based live coding environment. This live code editor is dedicated to manipulating
|
||
Strudel patterns while they play. The REPL features built-in visual feedback, which highlights which elements in
|
||
the patterned (mini-notation) sequences are influencing the event that is currently being played. This feedback is
|
||
designed to support both learning and live use of Strudel.
|
||
</p>
|
||
<p>
|
||
Besides a UI for playback control and meta information, the main part of the REPL interface is the code editor
|
||
powered by CodeMirror. In it, the user can edit and evaluate pattern code live, using one of the available
|
||
synthesis outputs to create music and/or sound art. The control flow of the REPL follows 3 basic steps:
|
||
</p>
|
||
<ol type="1">
|
||
<li>
|
||
The user writes and updates code. Each update transpiles and evaluates it to create a
|
||
<code>Pattern</code> instance
|
||
</li>
|
||
<li>
|
||
While the REPL is running, the <code>Scheduler</code> queries the active <code>Pattern</code> by a regular
|
||
interval, generating <code>Events</code> (also known as <code>Haps</code> in Strudel) for the next time span.
|
||
</li>
|
||
<li>
|
||
For each scheduling tick, all generated <code>Events</code> are triggered by calling their
|
||
<code>onTrigger</code> method, which is set by the output.
|
||
</li>
|
||
</ol>
|
||
<figure>
|
||
<img
|
||
src="https://github.com/tidalcycles/strudel/raw/talk/talk/public/strudelflow.png?raw=true"
|
||
style="width: 43%"
|
||
alt="REPL control flow"
|
||
/>
|
||
<figcaption aria-hidden="true">REPL control flow</figcaption>
|
||
</figure>
|
||
<h2 data-number="7.1" id="user-code"><span class="header-section-number">7.1</span> User Code</h2>
|
||
<p>To create a <code>Pattern</code> from the user code, two steps are needed:</p>
|
||
<ol type="1">
|
||
<li>Transpile the JS input code to make it functional</li>
|
||
<li>Evaluate the transpiled code</li>
|
||
</ol>
|
||
<h3 data-number="7.1.1" id="transpilation-evaluation">
|
||
<span class="header-section-number">7.1.1</span> Transpilation & Evaluation
|
||
</h3>
|
||
<p>
|
||
In the JavaScript world, using transpilation is a common practise to be able to use language features that are not
|
||
supported by the base language. Tools like <code>babel</code> will transpile code that contains unsupported
|
||
language features into a version of the code without those features.
|
||
</p>
|
||
<p>
|
||
In the same tradition, Strudel can add a transpilation step to simplify the user code in the context of live
|
||
coding. For example, the Strudel REPL lets the user create mini notation patterns using just double quoted
|
||
strings, while single quoted strings remain what they are:
|
||
</p>
|
||
<div class="sourceCode" id="cb7">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="st">"c3 [e3 g3]*2"</span></span></code></pre>
|
||
</div>
|
||
<p>is transpiled to:</p>
|
||
<div class="sourceCode" id="cb8">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a><span class="fu">mini</span>(<span class="st">"c3 [e3 g3]*2"</span>)<span class="op">.</span><span class="fu">withMiniLocation</span>([<span class="dv">1</span><span class="op">,</span><span class="dv">0</span><span class="op">,</span><span class="dv">0</span>]<span class="op">,</span>[<span class="dv">1</span><span class="op">,</span><span class="dv">14</span><span class="op">,</span><span class="dv">14</span>])</span></code></pre>
|
||
</div>
|
||
<p>
|
||
Here, the string is wrapped in <code>mini</code>, which will create a pattern from a mini notation string.
|
||
Additionally, the <code>withMiniLocation</code> method passes the original source code location of the string to
|
||
the pattern, which enables highlighting active events.
|
||
</p>
|
||
<p>
|
||
Other convenient features like pseudo variables, operator overloading and top level await are possible with
|
||
transpilation.
|
||
</p>
|
||
<p>After the transpilation, the code is ready to be evaluated into a <code>Pattern</code>.</p>
|
||
<p>
|
||
Behind the scenes, the user code string is parsed with <code>acorn</code>, turning it into an Abstract Syntax Tree
|
||
(AST). The AST allows changing the structure of the code before generating the transpiled version using
|
||
<code>escodegen</code>.
|
||
</p>
|
||
<h3 data-number="7.1.2" id="mini-notation"><span class="header-section-number">7.1.2</span> Mini Notation</h3>
|
||
<p>
|
||
While the transpilation allows JavaScript to express Patterns in a less verbose way, it is still preferable to use
|
||
the Mini Notation as a more compact way to express rhythm. Strudel aims to provide the same Mini Notation features
|
||
and syntax as used in Tidal.
|
||
</p>
|
||
<p>
|
||
The Mini Notation parser is implemented using <code>peggy</code>, which allows generating performant parsers for
|
||
Domain Specific Languages (DSLs) using a concise grammar notation. The generated parser turns the Mini Notation
|
||
string into an AST which is used to call the respective Strudel functions with the given structure. For example,
|
||
<code>"c3 [e3 g3]*2"</code> will result in the following calls:
|
||
</p>
|
||
<div class="sourceCode" id="cb9">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="fu">seq</span>(</span>
|
||
<span id="cb9-2"><a href="#cb9-2" aria-hidden="true" tabindex="-1"></a> <span class="fu">reify</span>(<span class="st">'c3'</span>)<span class="op">.</span><span class="fu">withLocation</span>([<span class="dv">1</span><span class="op">,</span><span class="dv">1</span><span class="op">,</span><span class="dv">1</span>]<span class="op">,</span> [<span class="dv">1</span><span class="op">,</span><span class="dv">4</span><span class="op">,</span><span class="dv">4</span>])<span class="op">,</span></span>
|
||
<span id="cb9-3"><a href="#cb9-3" aria-hidden="true" tabindex="-1"></a> <span class="fu">seq</span>(</span>
|
||
<span id="cb9-4"><a href="#cb9-4" aria-hidden="true" tabindex="-1"></a> <span class="fu">reify</span>(<span class="st">'e3'</span>)<span class="op">.</span><span class="fu">withLocation</span>([<span class="dv">1</span><span class="op">,</span><span class="dv">5</span><span class="op">,</span><span class="dv">5</span>]<span class="op">,</span> [<span class="dv">1</span><span class="op">,</span><span class="dv">8</span><span class="op">,</span><span class="dv">8</span>])<span class="op">,</span></span>
|
||
<span id="cb9-5"><a href="#cb9-5" aria-hidden="true" tabindex="-1"></a> <span class="fu">reify</span>(<span class="st">'g3'</span>)<span class="op">.</span><span class="fu">withLocation</span>([<span class="dv">1</span><span class="op">,</span><span class="dv">8</span><span class="op">,</span><span class="dv">8</span>]<span class="op">,</span> [<span class="dv">1</span><span class="op">,</span><span class="dv">10</span><span class="op">,</span><span class="dv">10</span>])<span class="op">,</span></span>
|
||
<span id="cb9-6"><a href="#cb9-6" aria-hidden="true" tabindex="-1"></a> )<span class="op">.</span><span class="fu">fast</span>(<span class="dv">2</span>)</span>
|
||
<span id="cb9-7"><a href="#cb9-7" aria-hidden="true" tabindex="-1"></a>)</span></code></pre>
|
||
</div>
|
||
<h3 data-number="7.1.3" id="highlighting-locations">
|
||
<span class="header-section-number">7.1.3</span> Highlighting Locations
|
||
</h3>
|
||
<p>
|
||
As seen in the examples above, both the JS and the Mini Notation parser add source code locations using
|
||
<code>withMiniLocation</code> and <code>withLocation</code> methods. While the JS parser adds locations relative
|
||
to the user code as a whole, the Mini Notation adds locations relative to the position of the mini notation
|
||
string. The absolute location of elements within Mini Notation can be calculated by simply adding both locations
|
||
together. This absolute location can be used to highlight active events in real time.
|
||
</p>
|
||
<h2 data-number="7.2" id="scheduling-events"><span class="header-section-number">7.2</span> Scheduling Events</h2>
|
||
<p>
|
||
After an instance of <code>Pattern</code> is obtained from the user code, it is used by the scheduler to get
|
||
queried for events. Once started, the scheduler runs at a fixed interval to query active pattern for events
|
||
withing the current interval’s time span. A simplified implementation looks like this:
|
||
</p>
|
||
<div class="sourceCode" id="cb10">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true" tabindex="-1"></a><span class="kw">let</span> pattern <span class="op">=</span> <span class="fu">seq</span>(<span class="st">'c3'</span><span class="op">,</span> [<span class="st">'e3'</span><span class="op">,</span> <span class="st">'g3'</span>])<span class="op">;</span> <span class="co">// pattern from user</span></span>
|
||
<span id="cb10-2"><a href="#cb10-2" aria-hidden="true" tabindex="-1"></a><span class="kw">let</span> interval <span class="op">=</span> <span class="fl">0.5</span><span class="op">;</span> <span class="co">// query interval in seconds</span></span>
|
||
<span id="cb10-3"><a href="#cb10-3" aria-hidden="true" tabindex="-1"></a><span class="kw">let</span> time <span class="op">=</span> <span class="dv">0</span><span class="op">;</span> <span class="co">// beginning of current time span</span></span>
|
||
<span id="cb10-4"><a href="#cb10-4" aria-hidden="true" tabindex="-1"></a><span class="kw">let</span> minLatency <span class="op">=</span> <span class="op">.</span><span class="dv">1</span><span class="op">;</span> <span class="co">// min time before a hap should trigger</span></span>
|
||
<span id="cb10-5"><a href="#cb10-5" aria-hidden="true" tabindex="-1"></a><span class="pp">setInterval</span>(() <span class="kw">=></span> {</span>
|
||
<span id="cb10-6"><a href="#cb10-6" aria-hidden="true" tabindex="-1"></a> <span class="kw">const</span> haps <span class="op">=</span> pattern<span class="op">.</span><span class="fu">queryArc</span>(time<span class="op">,</span> time <span class="op">+</span> interval)<span class="op">;</span></span>
|
||
<span id="cb10-7"><a href="#cb10-7" aria-hidden="true" tabindex="-1"></a> time <span class="op">+=</span> interval<span class="op">;</span> <span class="co">// increment time</span></span>
|
||
<span id="cb10-8"><a href="#cb10-8" aria-hidden="true" tabindex="-1"></a> haps<span class="op">.</span><span class="fu">forEach</span>((hap) <span class="kw">=></span> {</span>
|
||
<span id="cb10-9"><a href="#cb10-9" aria-hidden="true" tabindex="-1"></a> <span class="kw">const</span> deadline <span class="op">=</span> hap<span class="op">.</span><span class="at">whole</span><span class="op">.</span><span class="at">begin</span> <span class="op">-</span> time <span class="op">+</span> minLatency<span class="op">;</span></span>
|
||
<span id="cb10-10"><a href="#cb10-10" aria-hidden="true" tabindex="-1"></a> <span class="fu">onTrigger</span>(hap<span class="op">,</span> deadline<span class="op">,</span> duration)<span class="op">;</span></span>
|
||
<span id="cb10-11"><a href="#cb10-11" aria-hidden="true" tabindex="-1"></a> })<span class="op">;</span></span>
|
||
<span id="cb10-12"><a href="#cb10-12" aria-hidden="true" tabindex="-1"></a>}<span class="op">,</span> interval <span class="op">*</span> <span class="dv">1000</span>)<span class="op">;</span> <span class="co">// query each "interval" seconds</span></span></code></pre>
|
||
</div>
|
||
<p>
|
||
Note that the above code is simplified for illustrative purposes. The actual implementation has to work around
|
||
imprecise callbacks of <code>setInterval</code>. More about the implementation details can be read in
|
||
<a href="https://loophole-letters.vercel.app/web-audio-scheduling">this blog post</a>.
|
||
</p>
|
||
<p>
|
||
The fact that <code>Pattern.queryArc</code> is a pure function that maps a time span to a set of events allows us
|
||
to choose any interval we like without changing the resulting output. It also means that when the pattern is
|
||
changed from outside, the next scheduling callback will work with the new pattern, keeping its clock running.
|
||
</p>
|
||
<p>
|
||
The latency between the time the pattern is evaluated and the change is heard is between
|
||
<code>minLatency</code> and <code>interval + minLatency</code>, in our example between 100ms and 600ms. In
|
||
Strudel, the current query interval is 50ms with a minLatency of 100ms, meaning the latency is between 50ms and
|
||
150ms.
|
||
</p>
|
||
<h2 data-number="7.3" id="output"><span class="header-section-number">7.3</span> Output</h2>
|
||
<p>
|
||
The last step is to trigger each event in the chosen output. This is where the given time and value of each event
|
||
is used to generate audio or any other form of time based output. The default output of the Strudel REPL is the
|
||
WebAudio output. To understand what an output does, we first have to understand what control parameters are.
|
||
</p>
|
||
<h3 data-number="7.3.1" id="control-parameters">
|
||
<span class="header-section-number">7.3.1</span> Control Parameters
|
||
</h3>
|
||
<p>
|
||
To be able to manipulate multiple aspects of sound in parallel, so called control parameters are used to shape the
|
||
value of each event. Example:
|
||
</p>
|
||
<div class="sourceCode" id="cb11">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a><span class="fu">note</span>(<span class="st">"c3 e3"</span>)<span class="op">.</span><span class="fu">cutoff</span>(<span class="dv">1000</span>)<span class="op">.</span><span class="fu">s</span>(<span class="st">'sawtooth'</span>)</span>
|
||
<span id="cb11-2"><a href="#cb11-2" aria-hidden="true" tabindex="-1"></a> <span class="op">.</span><span class="fu">queryArc</span>(<span class="dv">0</span><span class="op">,</span> <span class="dv">1</span>)<span class="op">.</span><span class="fu">map</span>(hap <span class="kw">=></span> hap<span class="op">.</span><span class="at">value</span>)</span>
|
||
<span id="cb11-3"><a href="#cb11-3" aria-hidden="true" tabindex="-1"></a><span class="co">/* [</span></span>
|
||
<span id="cb11-4"><a href="#cb11-4" aria-hidden="true" tabindex="-1"></a><span class="co"> { note: 'c3', cutoff: 1000, s: 'sawtooth' }</span></span>
|
||
<span id="cb11-5"><a href="#cb11-5" aria-hidden="true" tabindex="-1"></a><span class="co"> { note: 'e3', cutoff: 1000, s: 'sawtooth' }</span></span>
|
||
<span id="cb11-6"><a href="#cb11-6" aria-hidden="true" tabindex="-1"></a><span class="co">] */</span></span></code></pre>
|
||
</div>
|
||
<p>
|
||
Here, the control parameter functions <code>note</code>, <code>cutoff</code> and <code>s</code> are used, where
|
||
each controls a different property in the value object. Each control parameter function accepts a primitive value,
|
||
a list of values to be sequenced into a <code>Pattern</code>, or a <code>Pattern</code>. In the example,
|
||
<code>note</code> gets a <code>Pattern</code> from a Mini Notation expression (double quoted), while
|
||
<code>cutoff</code> and <code>s</code> are given a <code>Number</code> and a (single quoted)
|
||
<code>String</code> respectively.
|
||
</p>
|
||
<p>
|
||
Strudel comes with a large default set of control parameter functions that are based on the ones used by Tidal and
|
||
SuperDirt, focusing on music and audio terminology. It is however possible to create custom control paramters for
|
||
any purpose:
|
||
</p>
|
||
<div class="sourceCode" id="cb12">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a><span class="kw">const</span> { x<span class="op">,</span> y } <span class="op">=</span> <span class="fu">createParams</span>(<span class="st">'x'</span><span class="op">,</span> <span class="st">'y'</span>)</span>
|
||
<span id="cb12-2"><a href="#cb12-2" aria-hidden="true" tabindex="-1"></a><span class="fu">x</span>(sine<span class="op">.</span><span class="fu">range</span>(<span class="dv">0</span><span class="op">,</span> <span class="dv">200</span>))<span class="op">.</span><span class="fu">y</span>(cosine<span class="op">.</span><span class="fu">range</span>(<span class="dv">0</span><span class="op">,</span><span class="dv">200</span>))</span></code></pre>
|
||
</div>
|
||
<p>
|
||
This example creates the custom control parameters <code>x</code> and <code>y</code> which are then used to form a
|
||
pattern that descibes the coordinates of a circle.
|
||
</p>
|
||
<h3 data-number="7.3.2" id="outputs"><span class="header-section-number">7.3.2</span> Outputs</h3>
|
||
<p>
|
||
Now that we know how the value of an event is manipulated using control parameters, we can look at how outputs can
|
||
use that value to generate anything. The scheduler above was calling the <code>onTrigger</code> function which is
|
||
used to implement the output. A very simple version of the web audio output could look like this:
|
||
</p>
|
||
<div class="sourceCode" id="cb13">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb13-1"><a href="#cb13-1" aria-hidden="true" tabindex="-1"></a><span class="kw">function</span> <span class="fu">onTrigger</span>(hap<span class="op">,</span> deadline<span class="op">,</span> duration) {</span>
|
||
<span id="cb13-2"><a href="#cb13-2" aria-hidden="true" tabindex="-1"></a> <span class="kw">const</span> { note } <span class="op">=</span> hap<span class="op">.</span><span class="at">value</span><span class="op">;</span></span>
|
||
<span id="cb13-3"><a href="#cb13-3" aria-hidden="true" tabindex="-1"></a> <span class="kw">const</span> time <span class="op">=</span> <span class="fu">getAudioContext</span>()<span class="op">.</span><span class="at">currentTime</span> <span class="op">+</span> deadline<span class="op">;</span></span>
|
||
<span id="cb13-4"><a href="#cb13-4" aria-hidden="true" tabindex="-1"></a> <span class="kw">const</span> o <span class="op">=</span> <span class="fu">getAudioContext</span>()<span class="op">.</span><span class="fu">createOscillator</span>()<span class="op">;</span></span>
|
||
<span id="cb13-5"><a href="#cb13-5" aria-hidden="true" tabindex="-1"></a> o<span class="op">.</span><span class="at">frequency</span><span class="op">.</span><span class="at">value</span> <span class="op">=</span> <span class="fu">getFreq</span>(note)<span class="op">;</span></span>
|
||
<span id="cb13-6"><a href="#cb13-6" aria-hidden="true" tabindex="-1"></a> o<span class="op">.</span><span class="fu">start</span>(time)<span class="op">;</span></span>
|
||
<span id="cb13-7"><a href="#cb13-7" aria-hidden="true" tabindex="-1"></a> o<span class="op">.</span><span class="fu">stop</span>(time <span class="op">+</span> <span class="bu">event</span><span class="op">.</span><span class="at">duration</span>)<span class="op">;</span></span>
|
||
<span id="cb13-8"><a href="#cb13-8" aria-hidden="true" tabindex="-1"></a> o<span class="op">.</span><span class="fu">connect</span>(<span class="fu">getAudioContext</span>()<span class="op">.</span><span class="at">destination</span>)<span class="op">;</span></span>
|
||
<span id="cb13-9"><a href="#cb13-9" aria-hidden="true" tabindex="-1"></a>}</span></code></pre>
|
||
</div>
|
||
<p>
|
||
The above example will create an <code>OscillatorNode</code> for each event, where the frequency is controlled by
|
||
the <code>note</code> param. In essence, this is how the WebAudio API output of Strudel works, only with many more
|
||
parameters to control synths, samples and effects.
|
||
</p>
|
||
<h1 data-number="8" id="pattern-alignment-and-combination">
|
||
<span class="header-section-number">8</span> Pattern alignment and combination
|
||
</h1>
|
||
<p>
|
||
One core aspect of Strudel, inherited from Tidal, is the flexible way that patterns can be combined, irrespective
|
||
of their structure. Its declarative approach means a live coder does not have to think about the details of
|
||
<em>how</em> this is done, only <em>what</em> is to be done.
|
||
</p>
|
||
<p>
|
||
As a simple example, consider two number patterns <code>"0 [1 2] 3"</code>, and <code>"10 20"</code>. The first
|
||
has three contiguous steps of equal lengths, with the second step broken down into two substeps, giving four
|
||
events in total. There are a very large number of ways in which the structure of these two patterns could be
|
||
combined, but the default method in both Strudel and Tidal is to line up the cycles of the two patterns, and then
|
||
take events from the first pattern and match them with those in the second pattern. Therefore, the following two
|
||
lines are equivalent:
|
||
</p>
|
||
<div class="sourceCode" id="cb14">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb14-1"><a href="#cb14-1" aria-hidden="true" tabindex="-1"></a><span class="st">"0 [1 2] 3"</span><span class="op">.</span><span class="fu">add</span>(<span class="st">"10 20"</span>)</span>
|
||
<span id="cb14-2"><a href="#cb14-2" aria-hidden="true" tabindex="-1"></a><span class="st">"10 [11 22] 23"</span></span></code></pre>
|
||
</div>
|
||
<p>
|
||
Where the events only partially overlap, they are treated as fragments of the event in the first pattern. This is
|
||
a little difficult to conceptualise, but lets start by comparing the two patterns in the following example:
|
||
</p>
|
||
<div class="sourceCode" id="cb15">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb15-1"><a href="#cb15-1" aria-hidden="true" tabindex="-1"></a><span class="st">"0 1 2"</span><span class="op">.</span><span class="fu">add</span>(<span class="st">"10 20"</span>)</span>
|
||
<span id="cb15-2"><a href="#cb15-2" aria-hidden="true" tabindex="-1"></a><span class="st">"10 [11 21] 20"</span></span></code></pre>
|
||
</div>
|
||
<p>
|
||
They are similar to the previous example in that the number <code>1</code> is split in two, with its two halves
|
||
added to <code>10</code> and <code>20</code> respectively. However, the <code>11</code> ‘remembers’ that it is a
|
||
fragment of that original <code>1</code> event, and so is treated as having a duration of a third of a cycle,
|
||
despite only being active for a sixth of a cycle. Likewise, the <code>21</code> is also a fragment of that
|
||
original <code>1</code> event, but a fragment of its second half. Because the start of its event is missing, it
|
||
wouldn’t actually trigger a sound (unless it underwent further pattern transformations/combinations).
|
||
</p>
|
||
<p>
|
||
In practice, the effect of this default, implicit method for combining two patterns is that the second pattern is
|
||
added <em>in</em> to the first one, and indeed this can be made explicit:
|
||
</p>
|
||
<div class="sourceCode" id="cb16">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb16-1"><a href="#cb16-1" aria-hidden="true" tabindex="-1"></a><span class="st">"0 1 2"</span><span class="op">.</span><span class="at">add</span><span class="op">.</span><span class="fu">in</span>(<span class="st">"10 20"</span>)</span></code></pre>
|
||
</div>
|
||
<p>This makes way for other ways to align the pattern, and several are already defined, in particular:</p>
|
||
<ul>
|
||
<li>
|
||
<code>in</code> - as explained above, aligns cycles, and applies values from the pattern on the right
|
||
<em>in</em> to the pattern on the left.
|
||
</li>
|
||
<li>
|
||
<code>out</code> - as with <code>in</code>, but values are applied <em>out</em> of the pattern on the left
|
||
(i.e. <em>in</em> to the one on the right).
|
||
</li>
|
||
<li>
|
||
<code>mix</code> - structures from both patterns are combined, so that the new events are not fragments but are
|
||
created at intersections of events from both sides.
|
||
</li>
|
||
<li>
|
||
<code>squeeze</code> - cycles from the pattern on the right are squeezed into events on the left. So that
|
||
e.g. <code>"0 1 2".add.squeeze("10 20")</code> is equivalent to <code>"[10 20] [11 21] [12 22]"</code>.
|
||
</li>
|
||
<li>
|
||
<code>squeezeout</code> - as with <code>squeeze</code>, but cycles from the left are squeezed into events on the
|
||
right. So, <code>"0 1 2".add.squeezeout("10 20")</code> is equivalent to <code>[10 11 12] [20 21 22]</code>.
|
||
</li>
|
||
<li>
|
||
<code>trig</code> is similar to <code>squeezeout</code> in that cycles from the right are aligned with events on
|
||
the left. However those cycles are not ‘squeezed’, rather they are truncated to fit the event. So
|
||
<code>"0 1 2 3 4 5 6 7".add.trig("10 [20 30]")</code> would be equivalent to
|
||
<code>10 11 12 13 20 21 30 31</code>. In effect, events on the right ‘trigger’ cycles on the left.
|
||
</li>
|
||
<li>
|
||
<code>trigzero</code> is similar to <code>trig</code>, but the pattern is ‘triggered’ from its very first cycle,
|
||
rather than from the current cycle. <code>trig</code> and <code>trigzero</code> therefore only give different
|
||
results where the leftmost pattern differs from one cycle to the next.
|
||
</li>
|
||
</ul>
|
||
<p>
|
||
We will save going deeper into the background, design and practicalities of these alignment functions for future
|
||
publications. However in the next section, we take them as a case study for looking at the different design
|
||
affordances offered by Haskell to Tidal, and JavaScript to Strudel.
|
||
</p>
|
||
<h1 data-number="9" id="comparing-strudel-and-haskell-in-use">
|
||
<span class="header-section-number">9</span> Comparing Strudel and Haskell in use
|
||
</h1>
|
||
<p>
|
||
Unlike Haskell, JavaScript lacks the ability to define custom infix operators, or change the meaning of existing
|
||
ones. So the above Strudel example of <code>"0 1 2".add.out("10 20")</code> is equivalent to the Tidal expression
|
||
<code>"0 1 2" +| "10 20"</code>, where the vertical bar in the operator <code>+|</code> stands for
|
||
<code>out</code> (where <code>a |+ b</code> would be equivalent of <code>a.add.in(b)</code>).
|
||
</p>
|
||
<p>
|
||
From this we can already see that Tidal tends towards brevity through mixing infix operators with functions, and
|
||
Strudel tends towards spelling out operations which are joined together with the <code>.</code> operator. This
|
||
then is the design trade-off of Tidal’s tersity, versus Strudel’s simplicity.
|
||
</p>
|
||
<p>To demonstrate this, consider the following Tidal pattern:</p>
|
||
<pre
|
||
class="tidal"
|
||
><code>iter 4 $ every 3 (||+ n "10 20") $ (n "0 1 3") # s "triangle" # crush 4</code></pre>
|
||
<p>This can be directly translated to the Strudel equivalent:</p>
|
||
<div class="sourceCode" id="cb18">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb18-1"><a href="#cb18-1" aria-hidden="true" tabindex="-1"></a><span class="fu">iter</span>(<span class="dv">4</span><span class="op">,</span> <span class="fu">every</span>(<span class="dv">3</span><span class="op">,</span> add<span class="op">.</span><span class="fu">squeeze</span>(<span class="st">"10 20"</span>)<span class="op">,</span> <span class="fu">n</span>(<span class="st">"0 1 3"</span>)<span class="op">.</span><span class="fu">s</span>(<span class="st">"triangle"</span>)<span class="op">.</span><span class="fu">crush</span>(<span class="dv">4</span>)))</span></code></pre>
|
||
</div>
|
||
<p>Although for a more canonical Strudel expression, we would reorder it as:</p>
|
||
<div class="sourceCode" id="cb19">
|
||
<pre
|
||
class="sourceCode js"
|
||
><code class="sourceCode javascript"><span id="cb19-1"><a href="#cb19-1" aria-hidden="true" tabindex="-1"></a><span class="fu">n</span>(<span class="st">"0 1 3"</span>)<span class="op">.</span><span class="fu">every</span>(<span class="dv">3</span><span class="op">,</span> add<span class="op">.</span><span class="fu">squeeze</span>(<span class="st">"10 20"</span>))<span class="op">.</span><span class="fu">iter</span>(<span class="dv">4</span>)<span class="op">.</span><span class="fu">s</span>(<span class="st">"triangle"</span>)<span class="op">.</span><span class="fu">crush</span>(<span class="dv">4</span>)</span></code></pre>
|
||
</div>
|
||
<p>
|
||
The Strudel example uses the <code>.</code> method call operator for all operations and combinations, whereas the
|
||
Tidal example has <code>#</code> for the default method for combining patterns and uses infix operators for other
|
||
methods. The lack of parenthesis in the Tidal example is partly due to the way that arguments are applied to
|
||
Haskell’s functions, and partly due to the use of the <code>$</code> operator as an alternative way to establish
|
||
precedence and control the order of evaluation.
|
||
</p>
|
||
<p>
|
||
Considering the above, we argue that the Haskell syntax is a little cleaner, but that the Strudel syntax is easier
|
||
to learn. Our informal observation is that while Haskell’s dollar <code>$</code> operator is very useful in making
|
||
code easier to work with, it is one of the most difficult aspects of Tidal use for beginners to learn. On the
|
||
other hand, the deeper levels of parenthesis in Strudel code can be difficult to keep track of, especially while
|
||
coding under pressure of live musical performance. However this difficulty can be largely be mitigated by
|
||
reordering expressions, and further mitigated by supporting editor features.
|
||
</p>
|
||
<p>
|
||
With Strudel, we have little choice but to embrace the affordances and constraints offered by JavaScript, and
|
||
while designing a domain-specific language entirely based on method calls is a challenge, through creative
|
||
adoption of functional programming techniques like partial application, we are so far very happy with the results.
|
||
Tidal’s functional reactive approach to pattern-making has in general translated well to JavaScript, and
|
||
opportunities and constraints have overall traded off to create a very approachable and useable live coding
|
||
environment.
|
||
</p>
|
||
<h2 data-number="9.1" id="the-trade-off-of-flexible-typing">
|
||
<span class="header-section-number">9.1</span> The trade-off of flexible typing
|
||
</h2>
|
||
<p>
|
||
We have identified one problem with porting Tidal to JavaScript where we have missed Haskell’s strict typing and
|
||
type inference. In both Tidal and Strudel, time is rational, where any point in time is represented as the ratio
|
||
of two integers. This allows representation of musical ratios such that are impossible to represent accurately
|
||
using the more common floating point numbers. However while libraries are available that support rational numbers
|
||
in JavaScript, the lack of strict typing means that it is easy to implement pattern methods where computationally
|
||
expensive conversion from floating point to rational numbers are performed late, and therefore often enough to
|
||
overload the CPUs, due to the large number of iterative calculations required to estimate a ratio for a given
|
||
floating point number. To mitigate this problem, we might consider moving to TypeScript in the future.
|
||
</p>
|
||
<h1 data-number="10" id="future-outlook"><span class="header-section-number">10</span> Future Outlook</h1>
|
||
<p>
|
||
The project is still young, with many features on the horizon. As general guiding principles, Strudel aims to be
|
||
</p>
|
||
<ol type="1">
|
||
<li>accessible</li>
|
||
<li>consistent with Tidal’s approach to pattern</li>
|
||
<li>modular and extensible</li>
|
||
</ol>
|
||
<p>
|
||
While Haskell’s type system makes it a great language for the ongoing development of Tidal’s inner representation
|
||
of pattern, JavaScript’s vibrant ecosystem, flexibility and accessibility makes it a great host for more ad-hoc
|
||
experiments, including interface design. For the future, it is planned to integrate additional alternative sound
|
||
engines such as Glicol <span class="citation" data-cites="lanChaosprintGlicol2022">(Lan [2020] 2022)</span> and
|
||
Faust
|
||
<span class="citation" data-cites="FaustProgrammingLanguage2022"
|
||
>(<em>Faust - Programming Language for Audio Applications and Plugins</em> [2016] 2022)</span
|
||
>. Strudel is already approaching feature parity with Tidal, but there are more Tidal functions to be ported, and
|
||
work to be done to improve compatibility with Tidal’s mininotation. Tidal version 2.0 is under development, which
|
||
brings a new representation for sequences to its patterns, which will then be brought to Strudel. Besides sound,
|
||
other ways to render events are being explored, such as graphical, and choreographic output. We are also looking
|
||
into alternative ways of editing patterns, including multi-user editing for network music, parsing a novel syntax
|
||
to escape the constraints of javascript, and developing hardware/e-textile interfaces. In summary, there is a lot
|
||
of fun ahead.
|
||
</p>
|
||
<h1 data-number="11" id="links"><span class="header-section-number">11</span> Links</h1>
|
||
<p>
|
||
The Strudel REPL is available at <a href="https://strudel.cc" class="uri">https://strudel.cc</a>, including an
|
||
interactive tutorial. The repository is at
|
||
<a href="https://github.com/tidalcycles/strudel" class="uri">https://github.com/tidalcycles/strudel</a>, all the
|
||
code is open source under the AGPL-3.0 License.
|
||
</p>
|
||
<h1 data-number="12" id="acknowledgments"><span class="header-section-number">12</span> Acknowledgments</h1>
|
||
<p>
|
||
Thanks to the Strudel and wider Tidal, live coding, WebAudio and free/open source software communities for
|
||
inspiration and support. Alex McLean’s work on this project is supported by a UKRI Future Leaders Fellowship
|
||
[grant number MR/V025260/1].
|
||
</p>
|
||
<h1 class="unnumbered" id="references">References</h1>
|
||
<div id="refs" class="references csl-bib-body hanging-indent" role="doc-bibliography">
|
||
<div id="ref-FaustProgrammingLanguage2022" class="csl-entry" role="doc-biblioentry">
|
||
<em>Faust - Programming Language for Audio Applications and Plugins</em>. (2016) 2022. C++. GRAME.
|
||
<a href="https://github.com/grame-cncm/faust">https://github.com/grame-cncm/faust</a>.
|
||
</div>
|
||
<div id="ref-jackHydra2022" class="csl-entry" role="doc-biblioentry">
|
||
Jack, Olivia. (2022) 2022. <em>Hydra</em>.
|
||
<a href="https://github.com/ojack/hydra">https://github.com/ojack/hydra</a>.
|
||
</div>
|
||
<div id="ref-lanChaosprintGlicol2022" class="csl-entry" role="doc-biblioentry">
|
||
Lan, Qichao. (2020) 2022. <em>Chaosprint/Glicol</em>. Rust.
|
||
<a href="https://github.com/chaosprint/glicol">https://github.com/chaosprint/glicol</a>.
|
||
</div>
|
||
<div id="ref-mcleanAlgorithmicPattern2020a" class="csl-entry" role="doc-biblioentry">
|
||
Mclean, Alex. 2020. <span>“Algorithmic Pattern.”</span> In
|
||
<em>Proceedings of the International Conference on New Interfaces for Musical Expression</em>, 265--270.
|
||
Birmingham, UK. <a href="https://zenodo.org/record/4813352">https://zenodo.org/record/4813352</a>.
|
||
</div>
|
||
<div id="ref-mcleanFeedforward2020" class="csl-entry" role="doc-biblioentry">
|
||
McLean, Alex. 2020. <span>“Feedforward.”</span> In
|
||
<em>Proceedings of New Interfaces for Musical Expression</em>. Birmingham.
|
||
<a href="https://zenodo.org/record/6353969">https://zenodo.org/record/6353969</a>.
|
||
</div>
|
||
<div id="ref-mcleanTidalVortexZero2022" class="csl-entry" role="doc-biblioentry">
|
||
McLean, Alex, Raphaël Forment, Sylvain Le Beux, and Damián Silvani. 2022. <span>“TidalVortex Zero.”</span> In
|
||
<em>Proceedings of the 7th International Conference on Live Coding</em>. Limerick, Ireland: Zenodo.
|
||
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