diff --git a/src/components/ModuleNode.jsx b/src/components/ModuleNode.jsx
index a7a1247..9116795 100644
--- a/src/components/ModuleNode.jsx
+++ b/src/components/ModuleNode.jsx
@@ -8,6 +8,20 @@ import KeyboardWidget from './KeyboardWidget.jsx';
 import SequencerWidget from './SequencerWidget.jsx';
 import PianoRollWidget from './PianoRollWidget.jsx';
 
+// Dynamic module widths for sequencer/pianoroll based on step/bar count
+function getModuleWidth(mod, type) {
+  if (type === 'sequencer') {
+    const numSteps = parseInt(mod?.params?.steps || '16');
+    return Math.max(200, numSteps * 18 + 20); // CELL_W=18 + padding
+  }
+  if (type === 'pianoroll') {
+    const bars = parseInt(mod?.params?.bars || '4');
+    const totalBeats = bars * 4;
+    return 24 + totalBeats * 30 + 20; // KEY_W + beats*BEAT_PX + padding
+  }
+  return undefined;
+}
+
 // Map input port names → the param name they modulate (for visual feedback)
 const PORT_TO_PARAM = {
   filter:     { cutoff: 'frequency' },
@@ -150,7 +164,7 @@ export default function ModuleNode({ mod, zoom, onStartConnect, onPortPosition }
       style={{
         left: mod.x * zoom, top: mod.y * zoom,
         transform: `scale(${zoom})`, transformOrigin: 'top left',
-        ...(mod.type === 'pianoroll' ? { width: 520 } : mod.type === 'sequencer' ? { width: 310 } : {}),
+        ...(mod.type === 'pianoroll' ? { width: getModuleWidth(mod, 'pianoroll') } : mod.type === 'sequencer' ? { width: getModuleWidth(mod, 'sequencer') } : {}),
       }}
       data-module-id={mod.id}
       onPointerDown={(e) => {
diff --git a/src/components/PianoRollWidget.jsx b/src/components/PianoRollWidget.jsx
index 2585d8a..9e22f36 100644
--- a/src/components/PianoRollWidget.jsx
+++ b/src/components/PianoRollWidget.jsx
@@ -79,7 +79,7 @@ const MARIO_MELODY = [
   { note: 71, start: 70*s,  duration: 2*s },   // B4
 ];
 
-const ROLL_W = 500;
+const BEAT_PX = 30; // pixels per beat — constant density regardless of bar count
 const ROLL_H = 200;
 const KEY_W = 24;
 const MIN_NOTE = 48; // C3
@@ -110,7 +110,8 @@ export default function PianoRollWidget({ moduleId }) {
   const notesRef = useRef(notes);
   notesRef.current = notes;
 
-  const beatW = (ROLL_W - KEY_W) / totalBeats;
+  const rollW = KEY_W + totalBeats * BEAT_PX;
+  const beatW = BEAT_PX;
 
   // Draw the piano roll
   const draw = useCallback(() => {
@@ -220,7 +221,7 @@ export default function PianoRollWidget({ moduleId }) {
       ctx.fillStyle = 'rgba(0,229,255,0.3)';
       ctx.fillRect(x, row * ROW_H, Math.max(nw, 2), ROW_H);
     }
-  }, [totalBeats, beatW, playPos]);
+  }, [totalBeats, beatW, playPos, rollW]);
 
   // Animation loop
   useEffect(() => {
@@ -415,7 +416,7 @@ export default function PianoRollWidget({ moduleId }) {
   }, [mod]);
 
   return (
-    <div style={{ width: ROLL_W }}>
+    <div style={{ width: rollW }}>
       {/* Mini toolbar */}
       <div style={{ display: 'flex', gap: 4, marginBottom: 3 }}>
         <button
@@ -453,9 +454,9 @@ export default function PianoRollWidget({ moduleId }) {
       </div>
       <canvas
         ref={canvasRef}
-        width={ROLL_W}
+        width={rollW}
         height={ROLL_H}
-        style={{ width: ROLL_W, height: ROLL_H, borderRadius: 4, cursor: tool === 'draw' ? 'crosshair' : 'pointer' }}
+        style={{ width: rollW, height: ROLL_H, borderRadius: 4, cursor: tool === 'draw' ? 'crosshair' : 'pointer' }}
         onPointerDown={handleMouseDown}
       />
     </div>