diff --git a/packages/codemirror/codemirror.mjs b/packages/codemirror/codemirror.mjs
index 6aac0c8a4..71e5c49ab 100644
--- a/packages/codemirror/codemirror.mjs
+++ b/packages/codemirror/codemirror.mjs
@@ -444,14 +444,16 @@ export class StrudelMirror {
       this.setFontSize(value);
     }
   }
-  setCode(code) {
-    const changes = {
-      from: 0,
-      to: this.editor.state.doc.length,
-      insert: code,
-    };
+  replaceCode(code, from, to) {
+    const changes = { from, to, insert: code };
     this.editor.dispatch({ changes });
   }
+  insertCode(code, position) {
+    this.replaceCode(code, position, position);
+  }
+  setCode(code) {
+    this.replaceCode(code, 0, this.editor.state.doc.length);
+  }
   // used for debugging but could serve other purposes
   getActiveWidgets() {
     return getActiveWidgets(this.editor);
diff --git a/packages/superdough/synth.mjs b/packages/superdough/synth.mjs
index 38ad643de..224936914 100644
--- a/packages/superdough/synth.mjs
+++ b/packages/superdough/synth.mjs
@@ -485,8 +485,10 @@ export function waveformN(partials, phases, type) {
     if (phase !== 0) {
       const c = Math.cos(PI2 * phase);
       const s = Math.sin(PI2 * phase);
-      R = c * R - s * I;
-      I = s * R + c * I;
+      const R0 = R;
+      const I0 = I;
+      R = c * R0 - s * I0;
+      I = s * R0 + c * I0;
     }
     real[n + 1] = R;
     imag[n + 1] = I;