diff --git a/editor/index.js b/editor/index.js
index 86dbcaf..45be8aa 100644
--- a/editor/index.js
+++ b/editor/index.js
@@ -527,22 +527,17 @@ async function showSaveDialog() {
         const numSamplesNeeded = sampleRate * numSeconds | 0;
         const numChannels = 2;
         const wavMaker = new WavMaker(sampleRate, numChannels);
-        const context = ByteBeatNode.createContext();
-        const stack = ByteBeatNode.createStack();
+        const context = await g_byteBeat.createContext();
+        const stack = await g_byteBeat.createStack();
         for (let i = 0; i < numSamplesNeeded; i += sampleRate) {
           const start = i;
           const end = Math.min(i + sampleRate, numSamplesNeeded);
-          const output = [
-            new Float32Array(end - start),
-            new Float32Array(end - start),
-          ];
-          for (let j = start; j < end; ++j) {
-            for (let ch = 0; ch < numChannels; ++ch) {
-              const s = g_byteBeat.getSampleForTime(j, context, stack, ch);
-              output[ch][j - i] = s;
-            }
+          const dataP = [];
+          for (let channel = 0; channel < numChannels; ++channel) {
+            dataP.push(g_byteBeat.getSamplesForTimeRange(start, end, end - start, context, stack, channel));
           }
-          wavMaker.addData(output);
+          const data = await Promise.all(dataP);
+          wavMaker.addData(data);
           await wait();
         }
         const blob = wavMaker.getWavBlob();
diff --git a/js/wavmaker.js b/js/wavmaker.js
index fcfa80f..30a4458 100644
--- a/js/wavmaker.js
+++ b/js/wavmaker.js
@@ -24,8 +24,8 @@ class WavMaker {
   }
   getWavBlob() {
     const {numSamples, numChannels, sampleRate, blobs} = this;
-    var output = new Uint8Array(44);
-    var view = new DataView(output.buffer);
+    const output = new Uint8Array(44);
+    const view = new DataView(output.buffer);
 
     writeString(view, 0, 'RIFF');                           // RIFF identifier
     view.setUint32(4, 36 + this.numSamples * 2, true);      // RIFF chunk length
@@ -39,7 +39,7 @@ class WavMaker {
     view.setUint16(32, numChannels * 2, true);              // block align (channel count * bytes per sample)
     view.setUint16(34, 16, true);                           // bits per sample
     writeString(view, 36, 'data');                          // data chunk identifier
-    view.setUint32(40, numSamples * numChannels* 2, true);  // data chunk length
+    view.setUint32(40, numSamples * numChannels * 2, true); // data chunk length
 
     return new Blob([new Blob([output]), ...blobs], {type: 'audio/wav'});
   }