diff --git a/index.js b/index.js
index de83689..01386f1 100644
--- a/index.js
+++ b/index.js
@@ -9,7 +9,8 @@ const audioCtx = new AudioContext();
 const frequencies = [];
 const holds = [];
 
-let globalVolume = 1.0;
+let globalVolume = new GainNode(audioCtx, {gain: 1.0});
+globalVolume.connect(audioCtx.destination);
 
 /*
  * TODO:
@@ -19,48 +20,90 @@ let globalVolume = 1.0;
  * - keyboard playing (qwerty)
  */
 
-function playNote(frequency, duration=86400) {
-    let currentGain = globalVolume;
-
-    const bassBoost = f => {
-        const t = Math.pow(f / 20000, 1/10);
-        const a = 1.0;
-        const b = 0.05;
-
-        return b * t + a * (1 - t);
-    };
-
-    const oscillators = [];
-
-    while (frequency < 20000) {
-        const oscillator = new OscillatorNode(audioCtx, {frequency});
-        const gain = new GainNode(audioCtx);
-
-        const g = bassBoost(frequency) * currentGain;
-        gain.gain.setValueAtTime(0, audioCtx.currentTime);
-        gain.gain.linearRampToValueAtTime(g, audioCtx.currentTime + 0.010);
-        gain.gain.linearRampToValueAtTime(0, audioCtx.currentTime + duration);
-
-        oscillator.connect(gain).connect(audioCtx.destination);
-        oscillator.start();
-
-        oscillators.push(oscillator);
-
-       // break;  // only one frequency for now
-
-        frequency *= 2;
-        currentGain *= 0.3;
+class Envelope {
+    constructor() {
+        this.envelope = new GainNode(audioCtx);
     }
 
-    const stop = () => {
-        for (let oscillator of oscillators) {
-            oscillator.stop();
+    hold(attack=0.040, decay=0.110, sustain=0.8) {
+        this.envelope.gain.setValueAtTime(0, audioCtx.currentTime);
+        this.envelope.gain.linearRampToValueAtTime(1.0, audioCtx.currentTime + attack);
+        this.envelope.gain.linearRampToValueAtTime(sustain, audioCtx.currentTime + decay);
+    }
+
+    release(release=0.200) {
+        this.envelope.gain.setTargetAtTime(0.0, audioCtx.currentTime + release, release/3);
+    }
+}
+
+function bassBoost(f) {
+    const t = Math.pow(f / 20000, 1/10);
+    const a = 1.0;
+    const b = 0.05;
+
+    return b * t + a * (1 - t);
+}
+
+class Voice {
+    constructor(baseFrequency) {
+        this.baseFrequency = baseFrequency;
+        this.oscillators = [];
+        this.envelope = new Envelope();
+
+        let frequency = baseFrequency;
+        let gain = 1.0;
+
+        while (frequency < 20000) {
+            const oscillator = new OscillatorNode(audioCtx, {frequency});
+            const volume = new GainNode(audioCtx, {gain: bassBoost(frequency) * gain});
+            oscillator
+                .connect(volume)
+                .connect(this.envelope.envelope)
+                .connect(globalVolume);
+
+            this.oscillators.push(oscillator);
+
+            frequency *= 2;
+            gain *= 0.3;
         }
-    };
+    }
 
-    setTimeout(stop, duration*1000);
+    play(duration=86400) {
+        this.start();
 
-    return stop;
+        setTimeout(() => {
+            this.stop();
+        }, duration * 1000);
+    }
+
+    start() {
+        this.envelope.hold();
+        for (let oscillator of this.oscillators) {
+            oscillator.start();
+        }
+    }
+
+    stop() {
+        this.envelope.release();
+        for (let oscillator of this.oscillators) {
+            //oscillator.stop(0.200);
+        }
+    }
+
+    tune(newBaseFrequency) {
+        const adjust = newBaseFrequency / this.baseFrequency;
+        this.baseFrequency = newBaseFrequency;
+
+        for (let oscillator of this.oscillators) {
+            oscillator.frequency.value *= adjust;
+        }
+    }
+}
+
+function playNote(frequency, duration=86400) {
+    const voice = new Voice(frequency);
+    voice.play(duration);
+    return voice;
 }
 
 function keyIndex(key) {
@@ -104,7 +147,9 @@ function updateOptions(key) {
 function onKeyClick(event) {
     const keySpan = event.srcElement;
     const key = keySpan.id;
-    playNote(noteFrequency(key), 0.5);
+    if (holds[keyIndex(key)] === undefined) {
+        playNote(noteFrequency(key), 0.5);
+    }
     updateOptions(key);
 
     keySpan.classList.add('playing');
@@ -157,7 +202,7 @@ function addHold(key) {
 function removeHold(key) {
     const index = keyIndex(key);
     if (holds[index] !== undefined) {
-        holds[index]();
+        holds[index].stop();
     }
     delete holds[index];
     document.getElementById(key).classList.remove('held');
@@ -166,8 +211,7 @@ function removeHold(key) {
 function refreshHolds() {
     for (let i = 0; i < holds.length; i++) {
         if (holds[i] !== undefined) {
-            holds[i]();
-            holds[i] = playNote(frequencies[i]);
+            holds[i].tune(frequencies[i]);
         }
     }
 }
@@ -191,9 +235,9 @@ function setupListeners() {
         }
     }
     const range = document.getElementById("range");
-    range.onchange = e => {
+    range.oninput = e => {
         const val = parseFloat(range.value);
-        globalVolume = val;
+        globalVolume.gain.value = val;
         refreshHolds();
     }
 }