diff --git a/.eslintrc b/.eslintrc
deleted file mode 100644
index 5be40e9..0000000
--- a/.eslintrc
+++ /dev/null
@@ -1,22 +0,0 @@
-{
-    "parser": "babel-eslint",
-    "rules": {
-        "curly": [2, "multi-line"],
-        "eol-last": [2],
-        "indent": [2, 4],
-        "linebreak-style": [2, "unix"],
-        "max-len": [2, 120, 4],
-        "no-trailing-spaces": [2, { "skipBlankLines": true }],
-        "no-unused-vars": [2, {"args": "after-used", "varsIgnorePattern": "^_"}],
-        "quotes": [2, "single"],
-        "semi": [2, "always"],
-        "space-before-function-paren": [2, "always"],
-        "strict": [2, "never"]
-    },
-    "env": {
-        "browser": true,
-        "es6": true,
-        "node": true
-    },
-    "extends": ["eslint:recommended"]
-}
diff --git a/.eslintrc.js b/.eslintrc.js
new file mode 100644
index 0000000..36ff570
--- /dev/null
+++ b/.eslintrc.js
@@ -0,0 +1,3 @@
+module.exports = {
+    extends: ['scratch', 'scratch/node']
+};
diff --git a/package.json b/package.json
index 2f90211..351192c 100644
--- a/package.json
+++ b/package.json
@@ -26,6 +26,7 @@
     "babel-loader": "^6.4.1",
     "babel-preset-es2015": "^6.24.1",
     "eslint": "^3.19.0",
+    "eslint-config-scratch": "^3.1.0",
     "json": "^9.0.6",
     "minilog": "^3.0.1",
     "soundfont-player": "0.10.5",
diff --git a/src/.eslintrc.js b/src/.eslintrc.js
new file mode 100644
index 0000000..bfdc88d
--- /dev/null
+++ b/src/.eslintrc.js
@@ -0,0 +1,5 @@
+module.exports = {
+    root: true,
+    extends: ['scratch', 'scratch/es6'],
+    env: {browser: true}
+};
diff --git a/src/ADPCMSoundDecoder.js b/src/ADPCMSoundDecoder.js
index 63d4baf..f9e855e 100644
--- a/src/ADPCMSoundDecoder.js
+++ b/src/ADPCMSoundDecoder.js
@@ -1,6 +1,6 @@
-var ArrayBufferStream = require('./ArrayBufferStream');
-var Tone = require('tone');
-var log = require('./log');
+const ArrayBufferStream = require('./ArrayBufferStream');
+const Tone = require('tone');
+const log = require('./log');
 
 /**
  * Decode wav audio files that have been compressed with the ADPCM format.
@@ -10,38 +10,37 @@ var log = require('./log');
  * https://github.com/LLK/scratch-flash/blob/master/src/sound/WAVFile.as
  * @constructor
  */
-function ADPCMSoundDecoder () {
-}
+const ADPCMSoundDecoder = function () {};
 
 /**
  * Decode an ADPCM sound stored in an ArrayBuffer and return a promise
  * with the decoded audio buffer.
  * @param  {ArrayBuffer} audioData - containing ADPCM encoded wav audio
- * @return {Tone.Buffer}
+ * @return {Tone.Buffer} the decoded audio buffer
  */
 ADPCMSoundDecoder.prototype.decode = function (audioData) {
 
-    return new Promise(function (resolve, reject) {
-        var stream = new ArrayBufferStream(audioData);
+    return new Promise((resolve, reject) => {
+        const stream = new ArrayBufferStream(audioData);
 
-        var riffStr = stream.readUint8String(4);
-        if (riffStr != 'RIFF') {
+        const riffStr = stream.readUint8String(4);
+        if (riffStr !== 'RIFF') {
             log.warn('incorrect adpcm wav header');
             reject();
         }
 
-        var lengthInHeader = stream.readInt32();
-        if ((lengthInHeader + 8) != audioData.byteLength) {
-            log.warn('adpcm wav length in header: ' + lengthInHeader + ' is incorrect');
+        const lengthInHeader = stream.readInt32();
+        if ((lengthInHeader + 8) !== audioData.byteLength) {
+            log.warn(`adpcm wav length in header: ${lengthInHeader} is incorrect`);
         }
 
-        var wavStr = stream.readUint8String(4);
-        if (wavStr != 'WAVE') {
+        const wavStr = stream.readUint8String(4);
+        if (wavStr !== 'WAVE') {
             log.warn('incorrect adpcm wav header');
             reject();
         }
 
-        var formatChunk = this.extractChunk('fmt ', stream);
+        const formatChunk = this.extractChunk('fmt ', stream);
         this.encoding = formatChunk.readUint16();
         this.channels = formatChunk.readUint16();
         this.samplesPerSecond = formatChunk.readUint32();
@@ -52,18 +51,18 @@ ADPCMSoundDecoder.prototype.decode = function (audioData) {
         this.samplesPerBlock = formatChunk.readUint16();
         this.adpcmBlockSize = ((this.samplesPerBlock - 1) / 2) + 4; // block size in bytes
 
-        var samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
+        const samples = this.imaDecompress(this.extractChunk('data', stream), this.adpcmBlockSize);
 
-        // todo: this line is the only place Tone is used here, should be possible to remove
-        var buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
+        // @todo this line is the only place Tone is used here, should be possible to remove
+        const buffer = Tone.context.createBuffer(1, samples.length, this.samplesPerSecond);
 
-        // todo: optimize this? e.g. replace the divide by storing 1/32768 and multiply?
-        for (var i=0; i<samples.length; i++) {
+        // @todo optimize this? e.g. replace the divide by storing 1/32768 and multiply?
+        for (let i = 0; i < samples.length; i++) {
             buffer.getChannelData(0)[i] = samples[i] / 32768;
         }
 
         resolve(buffer);
-    }.bind(this));
+    });
 };
 
 /**
@@ -95,14 +94,14 @@ ADPCMSoundDecoder.prototype.indexTable = [
 ADPCMSoundDecoder.prototype.extractChunk = function (chunkType, stream) {
     stream.position = 12;
     while (stream.position < (stream.getLength() - 8)) {
-        var typeStr = stream.readUint8String(4);
-        var chunkSize = stream.readInt32();
-        if (typeStr == chunkType) {
-            var chunk = stream.extract(chunkSize);
+        const typeStr = stream.readUint8String(4);
+        const chunkSize = stream.readInt32();
+        if (typeStr === chunkType) {
+            const chunk = stream.extract(chunkSize);
             return chunk;
-        } else {
-            stream.position += chunkSize;
         }
+        stream.position += chunkSize;
+
     }
 };
 
@@ -114,19 +113,22 @@ ADPCMSoundDecoder.prototype.extractChunk = function (chunkType, stream) {
  * @return {Int16Array} the uncompressed audio samples
  */
 ADPCMSoundDecoder.prototype.imaDecompress = function (compressedData, blockSize) {
-    var sample, step, code, delta;
-    var index = 0;
-    var lastByte = -1; // -1 indicates that there is no saved lastByte
-    var out = [];
+    let sample;
+    let step;
+    let code;
+    let delta;
+    let index = 0;
+    let lastByte = -1; // -1 indicates that there is no saved lastByte
+    const out = [];
 
     // Bail and return no samples if we have no data
     if (!compressedData) return out;
 
     compressedData.position = 0;
-    var a = 0;
-    while (a==0) {
-        if (((compressedData.position % blockSize) == 0) && (lastByte < 0)) { // read block header
-            if (compressedData.getBytesAvailable() == 0) break;
+    const a = 0;
+    while (a === 0) {
+        if (((compressedData.position % blockSize) === 0) && (lastByte < 0)) { // read block header
+            if (compressedData.getBytesAvailable() === 0) break;
             sample = compressedData.readInt16();
             index = compressedData.readUint8();
             compressedData.position++; // skip extra header byte
@@ -135,7 +137,7 @@ ADPCMSoundDecoder.prototype.imaDecompress = function (compressedData, blockSize)
         } else {
             // read 4-bit code and compute delta from previous sample
             if (lastByte < 0) {
-                if (compressedData.getBytesAvailable() == 0) break;
+                if (compressedData.getBytesAvailable() === 0) break;
                 lastByte = compressedData.readUint8();
                 code = lastByte & 0xF;
             } else {
@@ -159,7 +161,7 @@ ADPCMSoundDecoder.prototype.imaDecompress = function (compressedData, blockSize)
             out.push(sample);
         }
     }
-    var samples = Int16Array.from(out);
+    const samples = Int16Array.from(out);
     return samples;
 };
 
diff --git a/src/ArrayBufferStream.js b/src/ArrayBufferStream.js
index dfc1378..1eb13d8 100644
--- a/src/ArrayBufferStream.js
+++ b/src/ArrayBufferStream.js
@@ -8,10 +8,10 @@
  * @param {ArrayBuffer} arrayBuffer - array to use as a stream
  * @constructor
  */
-function ArrayBufferStream (arrayBuffer) {
+const ArrayBufferStream = function (arrayBuffer) {
     this.arrayBuffer = arrayBuffer;
     this.position = 0;
-}
+};
 
 /**
  * Return a new ArrayBufferStream that is a slice of the existing one
@@ -19,8 +19,8 @@ function ArrayBufferStream (arrayBuffer) {
  * @return {ArrayBufferStream} the extracted stream
  */
 ArrayBufferStream.prototype.extract = function (length) {
-    var slicedArrayBuffer = this.arrayBuffer.slice(this.position, this.position+length);
-    var newStream = new ArrayBufferStream(slicedArrayBuffer);
+    const slicedArrayBuffer = this.arrayBuffer.slice(this.position, this.position + length);
+    const newStream = new ArrayBufferStream(slicedArrayBuffer);
     return newStream;
 };
 
@@ -40,10 +40,10 @@ ArrayBufferStream.prototype.getBytesAvailable = function () {
 
 /**
  * Read an unsigned 8 bit integer from the stream
- * @return {number}
+ * @return {number} the next 8 bit integer in the stream
  */
 ArrayBufferStream.prototype.readUint8 = function () {
-    var val = new Uint8Array(this.arrayBuffer, this.position, 1)[0];
+    const val = new Uint8Array(this.arrayBuffer, this.position, 1)[0];
     this.position += 1;
     return val;
 };
@@ -52,13 +52,13 @@ ArrayBufferStream.prototype.readUint8 = function () {
  * Read a sequence of bytes of the given length and convert to a string.
  * This is a convenience method for use with short strings.
  * @param {number} length - the number of bytes to convert
- * @return {String} a String made by concatenating the chars in the input
+ * @return {string} a String made by concatenating the chars in the input
  */
 ArrayBufferStream.prototype.readUint8String = function (length) {
-    var arr = new Uint8Array(this.arrayBuffer, this.position, length);
+    const arr = new Uint8Array(this.arrayBuffer, this.position, length);
     this.position += length;
-    var str = '';
-    for (var i=0; i<arr.length; i++) {
+    let str = '';
+    for (let i = 0; i < arr.length; i++) {
         str += String.fromCharCode(arr[i]);
     }
     return str;
@@ -66,40 +66,40 @@ ArrayBufferStream.prototype.readUint8String = function (length) {
 
 /**
  * Read a 16 bit integer from the stream
- * @return {number}
+ * @return {number} the next 16 bit integer in the stream
  */
 ArrayBufferStream.prototype.readInt16 = function () {
-    var val = new Int16Array(this.arrayBuffer, this.position, 1)[0];
+    const val = new Int16Array(this.arrayBuffer, this.position, 1)[0];
     this.position += 2; // one 16 bit int is 2 bytes
     return val;
 };
 
 /**
  * Read an unsigned 16 bit integer from the stream
- * @return {number}
+ * @return {number} the next unsigned 16 bit integer in the stream
  */
 ArrayBufferStream.prototype.readUint16 = function () {
-    var val = new Uint16Array(this.arrayBuffer, this.position, 1)[0];
+    const val = new Uint16Array(this.arrayBuffer, this.position, 1)[0];
     this.position += 2; // one 16 bit int is 2 bytes
     return val;
 };
 
 /**
  * Read a 32 bit integer from the stream
- * @return {number}
+ * @return {number} the next 32 bit integer in the stream
  */
 ArrayBufferStream.prototype.readInt32 = function () {
-    var val = new Int32Array(this.arrayBuffer, this.position, 1)[0];
+    const val = new Int32Array(this.arrayBuffer, this.position, 1)[0];
     this.position += 4; // one 32 bit int is 4 bytes
     return val;
 };
 
 /**
  * Read an unsigned 32 bit integer from the stream
- * @return {number}
+ * @return {number} the next unsigned 32 bit integer in the stream
  */
 ArrayBufferStream.prototype.readUint32 = function () {
-    var val = new Uint32Array(this.arrayBuffer, this.position, 1)[0];
+    const val = new Uint32Array(this.arrayBuffer, this.position, 1)[0];
     this.position += 4; // one 32 bit int is 4 bytes
     return val;
 };
diff --git a/src/DrumPlayer.js b/src/DrumPlayer.js
index 6df833b..1532c16 100644
--- a/src/DrumPlayer.js
+++ b/src/DrumPlayer.js
@@ -1,16 +1,16 @@
-var SoundPlayer = require('./SoundPlayer');
-var Tone = require('tone');
+const SoundPlayer = require('./SoundPlayer');
+const Tone = require('tone');
 
 /**
  * A prototype for the drum sound functionality that can load drum sounds, play, and stop them.
  * @param {Tone.Gain} outputNode - a webAudio node that the drum sounds will send their output to
  * @constructor
  */
-function DrumPlayer (outputNode) {
+const DrumPlayer = function (outputNode) {
     this.outputNode = outputNode;
 
-    var baseUrl = 'https://raw.githubusercontent.com/LLK/scratch-audio/develop/sound-files/drums/';
-    var fileNames = [
+    const baseUrl = 'https://raw.githubusercontent.com/LLK/scratch-audio/develop/sound-files/drums/';
+    const fileNames = [
         'SnareDrum(1)',
         'BassDrum(1b)',
         'SideStick(1)',
@@ -33,12 +33,12 @@ function DrumPlayer (outputNode) {
 
     this.drumSounds = [];
 
-    for (var i=0; i<fileNames.length; i++) {
-        var url = baseUrl + fileNames[i] + '_22k.wav';
+    for (let i = 0; i < fileNames.length; i++) {
+        const url = `${baseUrl + fileNames[i]}_22k.wav`;
         this.drumSounds[i] = new SoundPlayer(this.outputNode);
         this.drumSounds[i].setBuffer(new Tone.Buffer(url));
     }
-}
+};
 
 /**
  * Play a drum sound.
@@ -56,7 +56,7 @@ DrumPlayer.prototype.play = function (drum, outputNode) {
  * Stop all drum sounds.
  */
 DrumPlayer.prototype.stopAll = function () {
-    for (var i=0; i<this.drumSounds.length; i++) {
+    for (let i = 0; i < this.drumSounds.length; i++) {
         this.drumSounds[i].stop();
     }
 };
diff --git a/src/InstrumentPlayer.js b/src/InstrumentPlayer.js
index 9a989bc..95cb8a8 100644
--- a/src/InstrumentPlayer.js
+++ b/src/InstrumentPlayer.js
@@ -1,5 +1,5 @@
-var Tone = require('tone');
-var Soundfont = require('soundfont-player');
+const Tone = require('tone');
+const Soundfont = require('soundfont-player');
 
 /**
  * A prototype for the instrument sound functionality that can play notes.
@@ -12,7 +12,7 @@ var Soundfont = require('soundfont-player');
  * @param {Tone.Gain} outputNode - a webAudio node that the instrument will send its output to
  * @constructor
  */
-function InstrumentPlayer (outputNode) {
+const InstrumentPlayer = function (outputNode) {
     this.outputNode = outputNode;
 
     // Instrument names used by Musyng Kite soundfont, in order to
@@ -24,7 +24,7 @@ function InstrumentPlayer (outputNode) {
         'music_box', 'steel_drums', 'marimba', 'lead_1_square', 'fx_4_atmosphere'];
 
     this.instruments = [];
-}
+};
 
 /**
  * Play a note for some number of seconds with a particular instrument.
@@ -37,13 +37,13 @@ function InstrumentPlayer (outputNode) {
  * @param  {number} vol - a volume level (0-100%)
  */
 InstrumentPlayer.prototype.playNoteForSecWithInstAndVol = function (note, sec, instrumentNum, vol) {
-    var gain = vol / 100;
+    const gain = vol / 100;
     this.loadInstrument(instrumentNum)
         .then(() => {
             this.instruments[instrumentNum].play(
                 note, Tone.context.currentTime, {
-                    duration : sec,
-                    gain : gain
+                    duration: sec,
+                    gain: gain
                 }
             );
         });
@@ -57,20 +57,20 @@ InstrumentPlayer.prototype.playNoteForSecWithInstAndVol = function (note, sec, i
 InstrumentPlayer.prototype.loadInstrument = function (instrumentNum) {
     if (this.instruments[instrumentNum]) {
         return Promise.resolve();
-    } else {
-        return Soundfont.instrument(Tone.context, this.instrumentNames[instrumentNum])
-            .then((inst) => {
+    }
+    return Soundfont.instrument(Tone.context, this.instrumentNames[instrumentNum])
+            .then(inst => {
                 inst.connect(this.outputNode);
                 this.instruments[instrumentNum] = inst;
             });
-    }
+
 };
 
 /**
  * Stop all notes being played on all instruments
  */
 InstrumentPlayer.prototype.stopAll = function () {
-    for (var i=0; i<this.instruments.length; i++) {
+    for (let i = 0; i < this.instruments.length; i++) {
         if (this.instruments[i]) {
             this.instruments[i].stop();
         }
diff --git a/src/SoundPlayer.js b/src/SoundPlayer.js
index 2afa3c0..ed6e4c2 100644
--- a/src/SoundPlayer.js
+++ b/src/SoundPlayer.js
@@ -1,17 +1,17 @@
-var Tone = require('tone');
-var log = require('./log');
+const Tone = require('tone');
+const log = require('./log');
 
 /**
  * A SoundPlayer stores an audio buffer, and plays it
  * @constructor
  */
-function SoundPlayer () {
+const SoundPlayer = function () {
     this.outputNode = null;
     this.buffer = new Tone.Buffer();
     this.bufferSource = null;
     this.playbackRate = 1;
     this.isPlaying = false;
-}
+};
 
 /**
  * Connect the SoundPlayer to an output node
@@ -23,7 +23,7 @@ SoundPlayer.prototype.connect = function (node) {
 
 /**
  * Set an audio buffer
- * @param {Tone.Buffer} buffer
+ * @param {Tone.Buffer} buffer Buffer to set
  */
 SoundPlayer.prototype.setBuffer = function (buffer) {
     this.buffer = buffer;
@@ -74,8 +74,8 @@ SoundPlayer.prototype.start = function () {
  * @return {Promise} a Promise that resolves when the sound finishes playing
  */
 SoundPlayer.prototype.finished = function () {
-    var storedContext = this;
-    return new Promise(function (resolve) {
+    const storedContext = this;
+    return new Promise(resolve => {
         storedContext.bufferSource.onended = function () {
             this.isPlaying = false;
             resolve();
diff --git a/src/effects/EchoEffect.js b/src/effects/EchoEffect.js
index 2dfd9bd..95b2b81 100644
--- a/src/effects/EchoEffect.js
+++ b/src/effects/EchoEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * An echo effect (aka 'delay effect' in audio terms)
@@ -8,7 +8,7 @@ var Tone = require('tone');
 * Clamped 0-100
 * @constructor
 */
-function EchoEffect () {
+const EchoEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
@@ -16,7 +16,7 @@ function EchoEffect () {
     this.delay = new Tone.FeedbackDelay(0.25, 0.5);
 
     this.effectSend.chain(this.delay, this.effectReturn);
-}
+};
 
 Tone.extend(EchoEffect, Tone.Effect);
 
@@ -30,14 +30,14 @@ EchoEffect.prototype.set = function (val) {
     this.value = this.clamp(this.value, 0, 100);
 
     // mute the effect if value is 0
-    if (this.value == 0) {
+    if (this.value === 0) {
         this.wet.value = 0;
     } else {
         this.wet.value = 0.5;
     }
 
-    var feedback = (this.value / 100) * 0.75;
-    this.delay.feedback.rampTo(feedback, 1/60);
+    const feedback = (this.value / 100) * 0.75;
+    this.delay.feedback.rampTo(feedback, 1 / 60);
 };
 
 /**
@@ -53,10 +53,10 @@ EchoEffect.prototype.changeBy = function (val) {
 * @param {number} input - the input to clamp
 * @param {number} min - the min value to clamp to
 * @param {number} max - the max value to clamp to
+* @return {number} the clamped value
 */
 EchoEffect.prototype.clamp = function (input, min, max) {
     return Math.min(Math.max(input, min), max);
 };
 
 module.exports = EchoEffect;
-
diff --git a/src/effects/FuzzEffect.js b/src/effects/FuzzEffect.js
index 9ed24e3..bae55b2 100644
--- a/src/effects/FuzzEffect.js
+++ b/src/effects/FuzzEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A fuzz effect (aka 'distortion effect' in audio terms)
@@ -7,7 +7,7 @@ var Tone = require('tone');
 * Clamped 0-100
 * @constructor
 */
-function FuzzEffect () {
+const FuzzEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
@@ -15,7 +15,7 @@ function FuzzEffect () {
     this.distortion = new Tone.Distortion(1);
 
     this.effectSend.chain(this.distortion, this.effectReturn);
-}
+};
 
 Tone.extend(FuzzEffect, Tone.Effect);
 
@@ -43,10 +43,10 @@ FuzzEffect.prototype.changeBy = function (val) {
 * @param {number} input - the input to clamp
 * @param {number} min - the min value to clamp to
 * @param {number} max - the max value to clamp to
+* @return {number} the clamped value
 */
 FuzzEffect.prototype.clamp = function (input, min, max) {
     return Math.min(Math.max(input, min), max);
 };
 
 module.exports = FuzzEffect;
-
diff --git a/src/effects/PanEffect.js b/src/effects/PanEffect.js
index a0950c5..03c29a3 100644
--- a/src/effects/PanEffect.js
+++ b/src/effects/PanEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A pan effect, which moves the sound to the left or right between the speakers
@@ -7,7 +7,7 @@ var Tone = require('tone');
 * Clamped -100 to 100
 * @constructor
 */
-function PanEffect () {
+const PanEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
@@ -15,7 +15,7 @@ function PanEffect () {
     this.panner = new Tone.Panner();
 
     this.effectSend.chain(this.panner, this.effectReturn);
-}
+};
 
 Tone.extend(PanEffect, Tone.Effect);
 
@@ -44,10 +44,10 @@ PanEffect.prototype.changeBy = function (val) {
 * @param {number} input - the input to clamp
 * @param {number} min - the min value to clamp to
 * @param {number} max - the max value to clamp to
+* @return {number} the clamped value
 */
 PanEffect.prototype.clamp = function (input, min, max) {
     return Math.min(Math.max(input, min), max);
 };
 
 module.exports = PanEffect;
-
diff --git a/src/effects/PitchEffect.js b/src/effects/PitchEffect.js
index d93c35a..f48e8f3 100644
--- a/src/effects/PitchEffect.js
+++ b/src/effects/PitchEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A pitch change effect, which changes the playback rate of the sound in order
@@ -18,12 +18,12 @@ var Tone = require('tone');
 * on one SoundPlayer or a group of them.
 * @constructor
 */
-function PitchEffect () {
+const PitchEffect = function () {
     this.value = 0; // effect value
     this.ratio = 1; // the playback rate ratio
 
     this.tone = new Tone();
-}
+};
 
 /**
 * Set the effect value
@@ -39,7 +39,7 @@ PitchEffect.prototype.set = function (val, players) {
 /**
 * Change the effect value
 * @param {number} val - the value to change the effect by
-* @param {Object} players - a dictionary of SoundPlayer objects indexed by md5
+* @param {object} players - a dictionary of SoundPlayer objects indexed by md5
 */
 PitchEffect.prototype.changeBy = function (val, players) {
     this.set(this.value + val, players);
@@ -58,7 +58,7 @@ PitchEffect.prototype.getRatio = function (val) {
 
 /**
 * Update a sound player's playback rate using the current ratio for the effect
-* @param {Object} player - a SoundPlayer object
+* @param {object} player - a SoundPlayer object
 */
 PitchEffect.prototype.updatePlayer = function (player) {
     player.setPlaybackRate(this.ratio);
@@ -71,7 +71,7 @@ PitchEffect.prototype.updatePlayer = function (player) {
 PitchEffect.prototype.updatePlayers = function (players) {
     if (!players) return;
 
-    for (var md5 in players) {
+    for (const md5 in players) {
         if (players.hasOwnProperty(md5)) {
             this.updatePlayer(players[md5]);
         }
@@ -79,4 +79,3 @@ PitchEffect.prototype.updatePlayers = function (players) {
 };
 
 module.exports = PitchEffect;
-
diff --git a/src/effects/ReverbEffect.js b/src/effects/ReverbEffect.js
index 2ad393a..43fa70c 100644
--- a/src/effects/ReverbEffect.js
+++ b/src/effects/ReverbEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A reverb effect, simulating reverberation in a room
@@ -7,7 +7,7 @@ var Tone = require('tone');
 * Clamped 0 to 100
 * @constructor
 */
-function ReverbEffect () {
+const ReverbEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
@@ -15,7 +15,7 @@ function ReverbEffect () {
     this.reverb = new Tone.Freeverb();
 
     this.effectSend.chain(this.reverb, this.effectReturn);
-}
+};
 
 Tone.extend(ReverbEffect, Tone.Effect);
 
@@ -44,10 +44,10 @@ ReverbEffect.prototype.changeBy = function (val) {
 * @param {number} input - the input to clamp
 * @param {number} min - the min value to clamp to
 * @param {number} max - the max value to clamp to
+* @return {number} the clamped value
 */
 ReverbEffect.prototype.clamp = function (input, min, max) {
     return Math.min(Math.max(input, min), max);
 };
 
 module.exports = ReverbEffect;
-
diff --git a/src/effects/RoboticEffect.js b/src/effects/RoboticEffect.js
index d2f9a41..b8ebc9a 100644
--- a/src/effects/RoboticEffect.js
+++ b/src/effects/RoboticEffect.js
@@ -1,5 +1,4 @@
-
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A "robotic" effect that adds a low-pitched buzzing to the sound, reminiscent of the
@@ -12,16 +11,16 @@ var Tone = require('tone');
 * Exterminate.
 * @constructor
 */
-function RoboticEffect () {
+const RoboticEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
 
-    var time = this._delayTimeForValue(100);
+    const time = this._delayTimeForValue(100);
     this.feedbackCombFilter = new Tone.FeedbackCombFilter(time, 0.9);
 
     this.effectSend.chain(this.feedbackCombFilter, this.effectReturn);
-}
+};
 
 Tone.extend(RoboticEffect, Tone.Effect);
 
@@ -33,15 +32,15 @@ RoboticEffect.prototype.set = function (val) {
     this.value = val;
 
     // mute the effect if value is 0
-    if (this.value == 0) {
+    if (this.value === 0) {
         this.wet.value = 0;
     } else {
         this.wet.value = 1;
     }
 
     // set delay time using the value
-    var time = this._delayTimeForValue(this.value);
-    this.feedbackCombFilter.delayTime.rampTo(time, 1/60);
+    const time = this._delayTimeForValue(this.value);
+    this.feedbackCombFilter.delayTime.rampTo(time, 1 / 60);
 };
 
 /**
@@ -60,10 +59,9 @@ RoboticEffect.prototype.changeBy = function (val) {
 * @returns {number} a delay time in seconds
 */
 RoboticEffect.prototype._delayTimeForValue = function (val) {
-    var midiNote = ((val - 100) / 10) + 36;
-    var freq = Tone.Frequency(midiNote, 'midi').eval();
+    const midiNote = ((val - 100) / 10) + 36;
+    const freq = Tone.Frequency(midiNote, 'midi').eval();
     return 1 / freq;
 };
 
 module.exports = RoboticEffect;
-
diff --git a/src/effects/WobbleEffect.js b/src/effects/WobbleEffect.js
index 13f5877..9b6b4d8 100644
--- a/src/effects/WobbleEffect.js
+++ b/src/effects/WobbleEffect.js
@@ -1,4 +1,4 @@
-var Tone = require('tone');
+const Tone = require('tone');
 
 /**
 * A wobble effect. In audio terms, it sounds like tremolo.
@@ -11,7 +11,7 @@ var Tone = require('tone');
 * Clamped 0 to 100
 * @constructor
 */
-function WobbleEffect () {
+const WobbleEffect = function () {
     Tone.Effect.call(this);
 
     this.value = 0;
@@ -21,7 +21,7 @@ function WobbleEffect () {
     this.wobbleLFO.connect(this.wobbleGain.gain);
 
     this.effectSend.chain(this.wobbleGain, this.effectReturn);
-}
+};
 
 Tone.extend(WobbleEffect, Tone.Effect);
 
@@ -36,7 +36,7 @@ WobbleEffect.prototype.set = function (val) {
 
     this.wet.value = this.value / 100;
 
-    this.wobbleLFO.frequency.rampTo(this.value / 10, 1/60);
+    this.wobbleLFO.frequency.rampTo(this.value / 10, 1 / 60);
 };
 
 /**
@@ -52,10 +52,10 @@ WobbleEffect.prototype.changeBy = function (val) {
 * @param {number} input - the input to clamp
 * @param {number} min - the min value to clamp to
 * @param {number} max - the max value to clamp to
+* @return {number} the clamped value
 */
 WobbleEffect.prototype.clamp = function (input, min, max) {
     return Math.min(Math.max(input, min), max);
 };
 
 module.exports = WobbleEffect;
-
diff --git a/src/index.js b/src/index.js
index 67ea9ed..7d20af5 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,213 +1,32 @@
-var log = require('./log');
-var Tone = require('tone');
+const log = require('./log');
+const Tone = require('tone');
 
-var PitchEffect = require('./effects/PitchEffect');
-var PanEffect = require('./effects/PanEffect');
+const PitchEffect = require('./effects/PitchEffect');
+const PanEffect = require('./effects/PanEffect');
 
-var RoboticEffect = require('./effects/RoboticEffect');
-var FuzzEffect = require('./effects/FuzzEffect');
-var EchoEffect = require('./effects/EchoEffect');
-var ReverbEffect = require('./effects/ReverbEffect');
+const RoboticEffect = require('./effects/RoboticEffect');
+const FuzzEffect = require('./effects/FuzzEffect');
+const EchoEffect = require('./effects/EchoEffect');
+const ReverbEffect = require('./effects/ReverbEffect');
 
-var SoundPlayer = require('./SoundPlayer');
-var ADPCMSoundDecoder = require('./ADPCMSoundDecoder');
-var InstrumentPlayer = require('./InstrumentPlayer');
-var DrumPlayer = require('./DrumPlayer');
+const SoundPlayer = require('./SoundPlayer');
+const ADPCMSoundDecoder = require('./ADPCMSoundDecoder');
+const InstrumentPlayer = require('./InstrumentPlayer');
+const DrumPlayer = require('./DrumPlayer');
 
 /**
  * @fileOverview Scratch Audio is divided into a single AudioEngine,
  * that handles global functionality, and AudioPlayers, belonging to individual sprites and clones.
  */
 
-/**
- * There is a single instance of the AudioEngine. It handles global audio properties and effects,
- * loads all the audio buffers for sounds belonging to sprites, and creates a single instrument player
- * and a drum player, used by all play note and play drum blocks.
- * @constructor
- */
-function AudioEngine () {
-
-    // create the global audio effects
-    this.roboticEffect = new RoboticEffect();
-    this.fuzzEffect = new FuzzEffect();
-    this.echoEffect = new EchoEffect();
-    this.reverbEffect = new ReverbEffect();
-
-    // chain the global effects to the output
-    this.input = new Tone.Gain();
-    this.input.chain (
-        this.roboticEffect, this.fuzzEffect, this.echoEffect, this.reverbEffect,
-        Tone.Master
-    );
-
-    // global tempo in bpm (beats per minute)
-    this.currentTempo = 60;
-
-    // instrument player for play note blocks
-    this.instrumentPlayer = new InstrumentPlayer(this.input);
-    this.numInstruments = this.instrumentPlayer.instrumentNames.length;
-
-    // drum player for play drum blocks
-    this.drumPlayer = new DrumPlayer(this.input);
-    this.numDrums = this.drumPlayer.drumSounds.length;
-
-    // a map of md5s to audio buffers, holding sounds for all sprites
-    this.audioBuffers = {};
-
-    // microphone, for measuring loudness, with a level meter analyzer
-    this.mic = null;
-    this.micMeter = null;
-}
-
-/**
- * Decode a sound, decompressing it into audio samples.
- * Store a reference to it the sound in the audioBuffers dictionary, indexed by md5
- * @param  {Object} sound - an object containing audio data and metadata for a sound
- * @property {Buffer} data - sound data loaded from scratch-storage.
- * @property {string} format - format type, either empty or adpcm.
- * @property {string} md5 - the MD5 and extension of the sound.
- * @returns {?Promise} - a promise which will resolve after the audio buffer is stored, or null on error.
- */
-AudioEngine.prototype.decodeSound = function (sound) {
-
-    var loaderPromise = null;
-
-    switch (sound.format) {
-    case '':
-        loaderPromise = Tone.context.decodeAudioData(sound.data.buffer);
-        break;
-    case 'adpcm':
-        loaderPromise = (new ADPCMSoundDecoder()).decode(sound.data.buffer);
-        break;
-    default:
-        return log.warn('unknown sound format', sound.format);
-    }
-
-    var storedContext = this;
-    return loaderPromise.then(
-        function (decodedAudio) {
-            storedContext.audioBuffers[sound.md5] = new Tone.Buffer(decodedAudio);
-        },
-        function (error) {
-            log.warn('audio data could not be decoded', error);
-        }
-    );
-};
-
-/**
- * An older version of the AudioEngine had this function to load all sounds
- * This is a stub to provide a warning when it is called
- * @todo remove this
- */
-AudioEngine.prototype.loadSounds = function () {
-    log.warn('The loadSounds function is no longer available. Please use Scratch Storage.');
-};
-
-/**
- * Play a note for a duration on an instrument with a volume
- * @param  {number} note - a MIDI note number
- * @param  {number} beats - a duration in beats
- * @param  {number} inst - an instrument number (0-indexed)
- * @param  {number} vol - a volume level (0-100%)
- * @return {Promise} a Promise that resolves after the duration has elapsed
- */
-AudioEngine.prototype.playNoteForBeatsWithInstAndVol = function (note, beats, inst, vol) {
-    var sec = this.beatsToSec(beats);
-    this.instrumentPlayer.playNoteForSecWithInstAndVol(note, sec, inst, vol);
-    return this.waitForBeats(beats);
-};
-
-/**
- * Convert a number of beats to a number of seconds, using the current tempo
- * @param  {number} beats
- * @return {number} seconds
- */
-AudioEngine.prototype.beatsToSec = function (beats) {
-    return (60 / this.currentTempo) * beats;
-};
-
-/**
- * Wait for some number of beats
- * @param  {number} beats
- * @return {Promise} a Promise that resolves after the duration has elapsed
- */
-AudioEngine.prototype.waitForBeats = function (beats) {
-    var storedContext = this;
-    return new Promise(function (resolve) {
-        setTimeout(function () {
-            resolve();
-        }, storedContext.beatsToSec(beats) * 1000);
-    });
-};
-
-/**
- * Set the global tempo in bpm (beats per minute)
- * @param {number} value - the new tempo to set
- */
-AudioEngine.prototype.setTempo = function (value) {
-    this.currentTempo = value;
-};
-
-/**
- * Change the tempo by some number of bpm (beats per minute)
- * @param  {number} value - the number of bpm to change the tempo by
- */
-AudioEngine.prototype.changeTempo = function (value) {
-    this.setTempo(this.currentTempo  + value);
-};
-
-/**
- * Get the current loudness of sound received by the microphone.
- * Sound is measured in RMS and smoothed.
- * @return {number} loudness scaled 0 to 100
- */
-AudioEngine.prototype.getLoudness = function () {
-    if (!this.mic) {
-        this.mic = new Tone.UserMedia();
-        this.micMeter = new Tone.Meter('level', 0.5);
-        this.mic.open();
-        this.mic.connect(this.micMeter);
-    }
-    if (this.mic && this.mic.state == 'started') {
-        return this.micMeter.value * 100;
-    } else {
-        return -1;
-    }
-};
-
-/**
- * Names of the audio effects.
- * @readonly
- * @enum {string}
- */
-AudioEngine.prototype.EFFECT_NAMES = {
-    pitch: 'pitch',
-    pan: 'pan',
-    echo: 'echo',
-    reverb: 'reverb',
-    fuzz: 'fuzz',
-    robot: 'robot'
-};
-
-/**
- * Create an AudioPlayer. Each sprite or clone has an AudioPlayer.
- * It includes a reference to the AudioEngine so it can use global
- * functionality such as playing notes.
- * @return {AudioPlayer}
- */
-AudioEngine.prototype.createPlayer = function () {
-    return new AudioPlayer(this);
-};
-
-
 /**
  * Each sprite or clone has an audio player
  * the audio player handles sound playback, volume, and the sprite-specific audio effects:
  * pitch and pan
- * @param {AudioEngine}
+ * @param {AudioEngine} audioEngine AudioEngine for player
  * @constructor
  */
-function AudioPlayer (audioEngine) {
+const AudioPlayer = function (audioEngine) {
 
     this.audioEngine = audioEngine;
 
@@ -226,7 +45,7 @@ function AudioPlayer (audioEngine) {
 
     // sound players that are currently playing, indexed by the sound's md5
     this.activeSoundPlayers = {};
-}
+};
 
 /**
  * Play a sound
@@ -245,7 +64,7 @@ AudioPlayer.prototype.playSound = function (md5) {
     }
 
     // create a new soundplayer to play the sound
-    var player = new SoundPlayer();
+    const player = new SoundPlayer();
     player.setBuffer(this.audioEngine.audioBuffers[md5]);
     player.connect(this.effectsNode);
     this.pitchEffect.updatePlayer(player);
@@ -255,7 +74,7 @@ AudioPlayer.prototype.playSound = function (md5) {
     this.activeSoundPlayers[md5] = player;
 
     // remove sounds that are not playing from the active sound players array
-    for (var id in this.activeSoundPlayers) {
+    for (const id in this.activeSoundPlayers) {
         if (this.activeSoundPlayers.hasOwnProperty(id)) {
             if (!this.activeSoundPlayers[id].isPlaying) {
                 delete this.activeSoundPlayers[id];
@@ -283,7 +102,7 @@ AudioPlayer.prototype.playDrumForBeats = function (drum, beats) {
  */
 AudioPlayer.prototype.stopAllSounds = function () {
     // stop all active sound players
-    for (var md5 in this.activeSoundPlayers) {
+    for (const md5 in this.activeSoundPlayers) {
         this.activeSoundPlayers[md5].stop();
     }
 
@@ -344,4 +163,185 @@ AudioPlayer.prototype.setVolume = function (value) {
     this.effectsNode.gain.value = value / 100;
 };
 
+
+/**
+ * There is a single instance of the AudioEngine. It handles global audio properties and effects,
+ * loads all the audio buffers for sounds belonging to sprites, and creates a single instrument player
+ * and a drum player, used by all play note and play drum blocks.
+ * @constructor
+ */
+const AudioEngine = function () {
+
+    // create the global audio effects
+    this.roboticEffect = new RoboticEffect();
+    this.fuzzEffect = new FuzzEffect();
+    this.echoEffect = new EchoEffect();
+    this.reverbEffect = new ReverbEffect();
+
+    // chain the global effects to the output
+    this.input = new Tone.Gain();
+    this.input.chain(
+        this.roboticEffect, this.fuzzEffect, this.echoEffect, this.reverbEffect,
+        Tone.Master
+    );
+
+    // global tempo in bpm (beats per minute)
+    this.currentTempo = 60;
+
+    // instrument player for play note blocks
+    this.instrumentPlayer = new InstrumentPlayer(this.input);
+    this.numInstruments = this.instrumentPlayer.instrumentNames.length;
+
+    // drum player for play drum blocks
+    this.drumPlayer = new DrumPlayer(this.input);
+    this.numDrums = this.drumPlayer.drumSounds.length;
+
+    // a map of md5s to audio buffers, holding sounds for all sprites
+    this.audioBuffers = {};
+
+    // microphone, for measuring loudness, with a level meter analyzer
+    this.mic = null;
+    this.micMeter = null;
+};
+
+/**
+ * Decode a sound, decompressing it into audio samples.
+ * Store a reference to it the sound in the audioBuffers dictionary, indexed by md5
+ * @param  {object} sound - an object containing audio data and metadata for a sound
+ * @property {Buffer} data - sound data loaded from scratch-storage.
+ * @property {string} format - format type, either empty or adpcm.
+ * @property {string} md5 - the MD5 and extension of the sound.
+ * @returns {?Promise} - a promise which will resolve after the audio buffer is stored, or null on error.
+ */
+AudioEngine.prototype.decodeSound = function (sound) {
+
+    let loaderPromise = null;
+
+    switch (sound.format) {
+    case '':
+        loaderPromise = Tone.context.decodeAudioData(sound.data.buffer);
+        break;
+    case 'adpcm':
+        loaderPromise = (new ADPCMSoundDecoder()).decode(sound.data.buffer);
+        break;
+    default:
+        return log.warn('unknown sound format', sound.format);
+    }
+
+    const storedContext = this;
+    return loaderPromise.then(
+        decodedAudio => {
+            storedContext.audioBuffers[sound.md5] = new Tone.Buffer(decodedAudio);
+        },
+        error => {
+            log.warn('audio data could not be decoded', error);
+        }
+    );
+};
+
+/**
+ * An older version of the AudioEngine had this function to load all sounds
+ * This is a stub to provide a warning when it is called
+ * @todo remove this
+ */
+AudioEngine.prototype.loadSounds = function () {
+    log.warn('The loadSounds function is no longer available. Please use Scratch Storage.');
+};
+
+/**
+ * Play a note for a duration on an instrument with a volume
+ * @param  {number} note - a MIDI note number
+ * @param  {number} beats - a duration in beats
+ * @param  {number} inst - an instrument number (0-indexed)
+ * @param  {number} vol - a volume level (0-100%)
+ * @return {Promise} a Promise that resolves after the duration has elapsed
+ */
+AudioEngine.prototype.playNoteForBeatsWithInstAndVol = function (note, beats, inst, vol) {
+    const sec = this.beatsToSec(beats);
+    this.instrumentPlayer.playNoteForSecWithInstAndVol(note, sec, inst, vol);
+    return this.waitForBeats(beats);
+};
+
+/**
+ * Convert a number of beats to a number of seconds, using the current tempo
+ * @param  {number} beats number of beats to convert to secs
+ * @return {number} seconds number of seconds `beats` will last
+ */
+AudioEngine.prototype.beatsToSec = function (beats) {
+    return (60 / this.currentTempo) * beats;
+};
+
+/**
+ * Wait for some number of beats
+ * @param  {number} beats number of beats to wait for
+ * @return {Promise} a Promise that resolves after the duration has elapsed
+ */
+AudioEngine.prototype.waitForBeats = function (beats) {
+    const storedContext = this;
+    return new Promise(resolve => {
+        setTimeout(() => {
+            resolve();
+        }, storedContext.beatsToSec(beats) * 1000);
+    });
+};
+
+/**
+ * Set the global tempo in bpm (beats per minute)
+ * @param {number} value - the new tempo to set
+ */
+AudioEngine.prototype.setTempo = function (value) {
+    this.currentTempo = value;
+};
+
+/**
+ * Change the tempo by some number of bpm (beats per minute)
+ * @param  {number} value - the number of bpm to change the tempo by
+ */
+AudioEngine.prototype.changeTempo = function (value) {
+    this.setTempo(this.currentTempo + value);
+};
+
+/**
+ * Get the current loudness of sound received by the microphone.
+ * Sound is measured in RMS and smoothed.
+ * @return {number} loudness scaled 0 to 100
+ */
+AudioEngine.prototype.getLoudness = function () {
+    if (!this.mic) {
+        this.mic = new Tone.UserMedia();
+        this.micMeter = new Tone.Meter('level', 0.5);
+        this.mic.open();
+        this.mic.connect(this.micMeter);
+    }
+    if (this.mic && this.mic.state === 'started') {
+        return this.micMeter.value * 100;
+    }
+    return -1;
+
+};
+
+/**
+ * Names of the audio effects.
+ * @readonly
+ * @enum {string}
+ */
+AudioEngine.prototype.EFFECT_NAMES = {
+    pitch: 'pitch',
+    pan: 'pan',
+    echo: 'echo',
+    reverb: 'reverb',
+    fuzz: 'fuzz',
+    robot: 'robot'
+};
+
+/**
+ * Create an AudioPlayer. Each sprite or clone has an AudioPlayer.
+ * It includes a reference to the AudioEngine so it can use global
+ * functionality such as playing notes.
+ * @return {AudioPlayer} new AudioPlayer instance
+ */
+AudioEngine.prototype.createPlayer = function () {
+    return new AudioPlayer(this);
+};
+
 module.exports = AudioEngine;
diff --git a/src/log.js b/src/log.js
index 9be8fac..da6ed3c 100644
--- a/src/log.js
+++ b/src/log.js
@@ -1,4 +1,4 @@
-var minilog = require('minilog');
+const minilog = require('minilog');
 minilog.enable();
 
 module.exports = minilog('scratch-audioengine');
diff --git a/webpack.config.js b/webpack.config.js
index 4ad8cfe..40ffb73 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -2,7 +2,7 @@ var path = require('path');
 
 module.exports = {
     entry: {
-        'dist': './src/index.js'
+        dist: './src/index.js'
     },
     output: {
         path: __dirname,