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TinyMusic.js
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TinyMusic.js
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(function( global ) {
/*
* Private stuffz
*/
var enharmonics = 'B#-C|C#-Db|D|D#-Eb|E-Fb|E#-F|F#-Gb|G|G#-Ab|A|A#-Bb|B-Cb',
middleC = 440 * Math.pow( Math.pow( 2, 1 / 12 ), -9 ),
numeric = /^[0-9.]+$/,
octaveOffset = 4,
space = /\s+/,
num = /(\d+)/,
offsets = {};
// populate the offset lookup (note distance from C, in semitones)
enharmonics.split('|').forEach(function( val, i ) {
val.split('-').forEach(function( note ) {
offsets[ note ] = i;
});
});
/*
* Note class
*
* new Note ('A4 q') === 440Hz, quarter note
* new Note ('- e') === 0Hz (basically a rest), eigth note
* new Note ('A4 es') === 440Hz, dotted eighth note (eighth + sixteenth)
* new Note ('A4 0.0125') === 440Hz, 32nd note (or any arbitrary
* divisor/multiple of 1 beat)
*
*/
// create a new Note instance from a string
function Note( str ) {
var couple = str.split( space );
// frequency, in Hz
this.frequency = Note.getFrequency( couple[ 0 ] ) || 0;
// duration, as a ratio of 1 beat (quarter note = 1, half note = 0.5, etc.)
this.duration = Note.getDuration( couple[ 1 ] ) || 0;
}
// convert a note name (e.g. 'A4') to a frequency (e.g. 440.00)
Note.getFrequency = function( name ) {
var couple = name.split( num ),
distance = offsets[ couple[ 0 ] ],
octaveDiff = ( couple[ 1 ] || octaveOffset ) - octaveOffset,
freq = middleC * Math.pow( Math.pow( 2, 1 / 12 ), distance );
return freq * Math.pow( 2, octaveDiff );
};
// convert a duration string (e.g. 'q') to a number (e.g. 1)
// also accepts numeric strings (e.g '0.125')
// and compund durations (e.g. 'es' for dotted-eight or eighth plus sixteenth)
Note.getDuration = function( symbol ) {
return numeric.test( symbol ) ? parseFloat( symbol ) :
symbol.toLowerCase().split('').reduce(function( prev, curr ) {
return prev + ( curr === 'w' ? 4 : curr === 'h' ? 2 :
curr === 'q' ? 1 : curr === 'e' ? 0.5 :
curr === 's' ? 0.25 : 0 );
}, 0 );
};
typeof module !== 'undefined' && ( module.exports = Note );
/*
* Sequence class
*/
// create a new Sequence
function Sequence( ac, tempo, arr ) {
this.ac = ac || new AudioContext();
this.createFxNodes();
this.tempo = tempo || 120;
this.loop = true;
this.smoothing = 0;
this.staccato = 0;
this.notes = [];
this.push.apply( this, arr || [] );
}
// create gain and EQ nodes, then connect 'em
Sequence.prototype.createFxNodes = function() {
var eq = [ [ 'bass', 100 ], [ 'mid', 1000 ], [ 'treble', 2500 ] ],
prev = this.gain = this.ac.createGain();
eq.forEach(function( config, filter ) {
filter = this[ config[ 0 ] ] = this.ac.createBiquadFilter();
filter.type = 'peaking';
filter.frequency.value = config[ 1 ];
prev.connect( prev = filter );
}.bind( this ));
prev.connect( this.ac.destination );
return this;
};
// accepts Note instances or strings (e.g. 'A4 e')
Sequence.prototype.push = function() {
Array.prototype.forEach.call( arguments, function( note ) {
this.notes.push( note instanceof Note ? note : new Note( note ) );
}.bind( this ));
return this;
};
// create a custom waveform as opposed to "sawtooth", "triangle", etc
Sequence.prototype.createCustomWave = function( real, imag ) {
// Allow user to specify only one array and dupe it for imag.
if ( !imag ) {
imag = real;
}
// Wave type must be custom to apply period wave.
this.waveType = 'custom';
// Reset customWave
this.customWave = [ new Float32Array( real ), new Float32Array( imag ) ];
};
// recreate the oscillator node (happens on every play)
Sequence.prototype.createOscillator = function() {
this.stop();
this.osc = this.ac.createOscillator();
// customWave should be an array of Float32Arrays. The more elements in
// each Float32Array, the dirtier (saw-like) the wave is
if ( this.customWave ) {
this.osc.setPeriodicWave(
this.ac.createPeriodicWave.apply( this.ac, this.customWave )
);
} else {
this.osc.type = this.waveType || 'square';
}
this.osc.connect( this.gain );
return this;
};
// schedules this.notes[ index ] to play at the given time
// returns an AudioContext timestamp of when the note will *end*
Sequence.prototype.scheduleNote = function( index, when ) {
var duration = 60 / this.tempo * this.notes[ index ].duration,
cutoff = duration * ( 1 - ( this.staccato || 0 ) );
this.setFrequency( this.notes[ index ].frequency, when );
if ( this.smoothing && this.notes[ index ].frequency ) {
this.slide( index, when, cutoff );
}
this.setFrequency( 0, when + cutoff );
return when + duration;
};
// get the next note
Sequence.prototype.getNextNote = function( index ) {
return this.notes[ index < this.notes.length - 1 ? index + 1 : 0 ];
};
// how long do we wait before beginning the slide? (in seconds)
Sequence.prototype.getSlideStartDelay = function( duration ) {
return duration - Math.min( duration, 60 / this.tempo * this.smoothing );
};
// slide the note at <index> into the next note at the given time,
// and apply staccato effect if needed
Sequence.prototype.slide = function( index, when, cutoff ) {
var next = this.getNextNote( index ),
start = this.getSlideStartDelay( cutoff );
this.setFrequency( this.notes[ index ].frequency, when + start );
this.rampFrequency( next.frequency, when + cutoff );
return this;
};
// set frequency at time
Sequence.prototype.setFrequency = function( freq, when ) {
this.osc.frequency.setValueAtTime( freq, when );
return this;
};
// ramp to frequency at time
Sequence.prototype.rampFrequency = function( freq, when ) {
this.osc.frequency.linearRampToValueAtTime( freq, when );
return this;
};
// run through all notes in the sequence and schedule them
Sequence.prototype.play = function( when ) {
when = typeof when === 'number' ? when : this.ac.currentTime;
this.createOscillator();
this.osc.start( when );
this.notes.forEach(function( note, i ) {
when = this.scheduleNote( i, when );
}.bind( this ));
this.osc.stop( when );
this.osc.onended = this.loop ? this.play.bind( this, when ) : null;
return this;
};
// stop playback, null out the oscillator, cancel parameter automation
Sequence.prototype.stop = function() {
if ( this.osc ) {
this.osc.onended = null;
this.osc.disconnect();
this.osc = null;
}
return this;
};
typeof module !== 'undefined' && ( module.exports = Sequence );
global.Note = Note;
global.Sequence = Sequence;
}( typeof window !== 'undefined' ? window : this ) );