diff --git a/features/preview/synth.ts b/features/preview/synth.ts
index 8aa2ec4..293fc1d 100644
--- a/features/preview/synth.ts
+++ b/features/preview/synth.ts
@@ -17,15 +17,26 @@ export type Synthesizer = {
   changeChip: (chip: AvailableChip) => void;
 };
 
-const RING_BUFFER_SIZE = 8192;
-const RING_BUFFER_CHANNELS = 2;
-const RING_BUFFER_BYTE_SIZE =
-  RING_BUFFER_SIZE * RING_BUFFER_CHANNELS * Float32Array.BYTES_PER_ELEMENT;
-const RING_BUFFER_READ_POS_SIZE = Int32Array.BYTES_PER_ELEMENT;
-const RING_BUFFER_WRITE_POS_SIZE = Int32Array.BYTES_PER_ELEMENT;
-const RING_BUFFER_CONTROLS_SIZE =
-  RING_BUFFER_READ_POS_SIZE + RING_BUFFER_WRITE_POS_SIZE;
-const SAB_SIZE = RING_BUFFER_CONTROLS_SIZE + RING_BUFFER_BYTE_SIZE;
+function calculateRingBufferSize(
+  time: number,
+  sampleRate: number
+): {
+  sabSize: number;
+  bufferSize: number;
+} {
+  const RING_BUFFER_READ_POS_SIZE = Int32Array.BYTES_PER_ELEMENT;
+  const RING_BUFFER_WRITE_POS_SIZE = Int32Array.BYTES_PER_ELEMENT;
+  const RING_BUFFER_CONTROLS_SIZE =
+    RING_BUFFER_READ_POS_SIZE + RING_BUFFER_WRITE_POS_SIZE;
+
+  const RING_BUFFER_CHANNELS = 2;
+
+  const bufferSize = Math.floor(time * sampleRate);
+  const ringBufferSize =
+    bufferSize * RING_BUFFER_CHANNELS * Float32Array.BYTES_PER_ELEMENT;
+  const sabSize = RING_BUFFER_CONTROLS_SIZE + ringBufferSize;
+  return { sabSize, bufferSize };
+}
 
 type KeyOnWorkerRequestMessage = {
   type: "keyOn";
@@ -140,7 +151,6 @@ export function useSynthesizer() {
        *
        * It is necessary to use Atomics API to read and write positions.
        */
-      const sab = new SharedArrayBuffer(SAB_SIZE);
 
       const wasmWorker = new Worker("/worker/worker.js");
       const audioContext = new AudioContext();
@@ -151,6 +161,9 @@ export function useSynthesizer() {
       });
       synthNode.connect(audioContext.destination);
 
+      const { sabSize } = calculateRingBufferSize(0.2, audioContext.sampleRate);
+      const sab = new SharedArrayBuffer(sabSize);
+
       // Setup message handlers.
       wasmWorker.onmessage = async ({
         data,
diff --git a/public/worker/worker.js b/public/worker/worker.js
index ff2e79d..6b8dcf2 100644
--- a/public/worker/worker.js
+++ b/public/worker/worker.js
@@ -80,7 +80,7 @@ function handleInitialize(sampleRate, sab) {
     control.byteLength + leftBuffer.byteLength,
     bufferSize
   );
-  fillThreshold = (bufferSize * 3) / 4;
+  fillThreshold = bufferSize / 2;
 
   self.postMessage({
     type: "initialized",
@@ -177,8 +177,8 @@ function handleGenerate() {
   let nWritables = (readPos + bufferSize - 1 - writePos) % bufferSize;
 
   if (nWritables < fillThreshold) {
-    const TIMEOUT = 50;
-    Atomics.wait(control, SAB_READ_POSITION_INDEX, readPos, TIMEOUT);
+    const TIMEOUT_MSEC = 50;
+    Atomics.wait(control, SAB_READ_POSITION_INDEX, readPos, TIMEOUT_MSEC);
     return;
   }
 
diff --git a/public/worklet/processor.js b/public/worklet/processor.js
index db0d1ab..6aebab6 100644
--- a/public/worklet/processor.js
+++ b/public/worklet/processor.js
@@ -74,17 +74,22 @@ class SynthProcessor extends AudioWorkletProcessor {
     const nReadables = (writePos + this.bufferSize - readPos) % this.bufferSize;
 
     let nReads = Math.min(leftChannel.length, nReadables);
+    // if (nReads !== leftChannel.length) {
+    //   console.warn("buffer underrun!", leftChannel.length - nReads);
+    // }
 
     let pos = readPos;
+    let destOffset = 0;
     while (nReads > 0) {
       const chunk = Math.min(nReads, this.bufferSize - pos);
       const end = pos + chunk;
 
-      leftChannel.set(this.leftBuffer.subarray(pos, end));
-      rightChannel.set(this.rightBuffer.subarray(pos, end));
+      leftChannel.set(this.leftBuffer.subarray(pos, end), destOffset);
+      rightChannel.set(this.rightBuffer.subarray(pos, end), destOffset);
 
       nReads -= chunk;
       pos = end % this.bufferSize;
+      destOffset += chunk;
     }
 
     // It is unnecessary to fill zero-samples in buffer-underrun