refactor uses of voicings

+ fix usages of scaleTranspose

tutorial/test/__snapshots__/examples.test.mjs.snap

@@ -2352,6 +2352,15 @@ exports[`runs examples > example "room" example index 0 1`] = `
 ]
 `;
 
+exports[`runs examples > example "rootNotes" example index 0 1`] = `
+[
+  "[ 0/1 → 1/1 | note:C2 ]",
+  "[ 1/1 → 2/1 | note:A2 ]",
+  "[ 2/1 → 3/1 | note:D2 ]",
+  "[ 3/1 → 4/1 | note:G2 ]",
+]
+`;
+
 exports[`runs examples > example "round" example index 0 1`] = `
 [
   "[ 0/1 → 1/3 | note:D3 ]",

tutorial/tutorial.mdx

@@ -769,7 +769,7 @@ Together with layer, struct and voicings, this can be used to create a basic bac
 
 <MiniRepl
   tune={`"<C^7 A7b13 Dm7 G7>".layer(
-  x => x.voicings(['d3','g4']).struct("~ x").note(),
+  x => x.voicings('lefthand').struct("~ x").note(),
   x => x.rootNotes(2).note().s('sawtooth').cutoff(800)
 )`}
 />