fix: add .piano function

packages/repl/prebake.mjs

@@ -1,4 +1,4 @@
-import { controls, evalScope } from '@strudel.cycles/core';
+import { controls, noteToMidi, valueToMidi, Pattern, evalScope } from '@strudel.cycles/core';
 import { registerSynthSounds, registerZZFXSounds, samples } from '@strudel.cycles/webaudio';
 import * as core from '@strudel.cycles/core';
 
@@ -37,3 +37,18 @@ export async function prebake() {
     samples(`${ds}/vcsl.json`),
   ]);
 }
+
+const maxPan = noteToMidi('C8');
+const panwidth = (pan, width) => pan * width + (1 - width) / 2;
+
+Pattern.prototype.piano = function () {
+  return this.fmap((v) => ({ ...v, clip: v.clip ?? 1 })) // set clip if not already set..
+    .s('piano')
+    .release(0.1)
+    .fmap((value) => {
+      const midi = valueToMidi(value);
+      // pan by pitch
+      const pan = panwidth(Math.min(Math.round(midi) / maxPan, 1), 0.5);
+      return { ...value, pan: (value.pan || 1) * pan };
+    });
+};