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Synthesis

Make sound from nothing: oscillators, noise, envelopes, sweeps and drums.

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Make sound from nothing: oscillators, noise, envelopes, sweeps and drums.

audioFreq

Convert a note name or MIDI number to a frequency in Hz

audioFreq( note )

Argument	Type	Default
`note`	any	required	A note name such as C4, F#3 or Bb2 (C4 is middle C), or a MIDI note number where 69 is A4. Fractions detune, 60.1 is ten cents above C4.

Returns The frequency in Hz with A4 tuned to 440.

Generate a tone with an oscillator

audioOsc( shape, freq, seconds, sampleRate=44100, harmonics=16, partials, width=0.5, phase=0 )

Argument	Type	Default
`shape`	string	required	sine, saw, square, triangle, pulse or additive. Saw, square and triangle are band limited so they do not alias. Pulse is the naive digital kind used by chiptune hardware.
`freq`	double	required	The frequency in Hz, see audioFreq() for note names.
`seconds`	double	required	The length in seconds.
`sampleRate`	integer	`44100`	The sample rate in Hz. Defaults to 44100.
`harmonics`	integer	`16`	For saw, square and triangle: the most harmonics to add, fewer are used near the Nyquist frequency. Fewer harmonics sound duller. Defaults to 16.
`partials`	array	optional	For additive: an array of [ frequency multiple, amplitude ] pairs, for example [ [ 1, 1.0 ], [ 2, 0.5 ] ]. Amplitudes are used as given.
`width`	double	`0.5`	For pulse: the fraction of the cycle spent high, 0.5 is a square. NES style duties are 0.125, 0.25, 0.5 and 0.75. Defaults to 0.5.
`phase`	double	`0`	Where in the cycle to start, 0 to 1. Defaults to 0.

Returns A mono audio buffer with a peak of about 1.

Generate a sine that glides from one pitch to another

audioSweep( startHz, endHz, seconds, speed=28, sampleRate=44100 )

Argument	Type	Default
`startHz`	double	required	The frequency at the start, in Hz.
`endHz`	double	required	The frequency it settles towards, in Hz.
`seconds`	double	required	The length in seconds.
`speed`	double	`28`	How fast it settles, in 1/seconds. Higher is quicker. Defaults to 28.
`sampleRate`	integer	`44100`	The sample rate in Hz. Defaults to 44100.

Returns A mono audio buffer. Shape it with audioEnvelope() to make a kick or a laser.

Generate repeatable noise

audioNoise( seconds, sampleRate=44100, seed=1, color="white" )

Argument	Type	Default
`seconds`	double	required	The length in seconds.
`sampleRate`	integer	`44100`	The sample rate in Hz. Defaults to 44100.
`seed`	long	`1`	Seed for the random generator. The same seed always gives the same noise. Defaults to 1.
`color`	string	`"white"`	white (flat), pink (softer highs), brown (rumble) or blue (hissy highs). Defaults to white.

Returns A mono audio buffer at an RMS level of 0.25.

Shape the volume of a sound with an attack and an exponential decay

audioEnvelope( audio, attack=0.005, decay=0 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`attack`	double	`0.005`	Seconds to rise from silence to full volume in a straight line. 0 starts at full volume. Defaults to 0.005.
`decay`	double	`0`	The decay time constant in seconds, the level falls to 37% after one decay time. 0 means no decay. Defaults to 0.

Returns A new audio buffer.

Synthesise a drum hit

audioDrum( type, sampleRate=44100, seed=1, pitch=1, decay=1, level=1, seconds=1 )

Argument	Type	Default
`type`	string	required	kick, snare, hat, openhat, clap, tom, crash or riser.
`sampleRate`	integer	`44100`	The sample rate in Hz. Defaults to 44100.
`seed`	long	`1`	Seed for the noise, the same seed always gives the same hit. Defaults to 1.
`pitch`	double	`1`	Multiplier for the tuned part of kick, snare and tom. 1 is the default tuning, 0.8 is lower.
`decay`	double	`1`	Multiplier for how long the hit rings. 1 is the default, 2 is twice as long.
`level`	double	`1`	The peak level of the result, 0 to 1. Defaults to 1.
`seconds`	double	`1`	The length of a riser. Ignored by the other types.

Returns A mono audio buffer.

Filter an audio buffer with a low-pass, high-pass, band-pass or notch filter

audioFilter( audio, type, cutoff, q=0.7071 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`type`	string	required	lowpass, highpass, bandpass or notch.
`cutoff`	double	required	The corner or center frequency in Hz.
`q`	double	`0.7071`	Resonance. 0.7071 is flat, higher peaks at the cutoff. For bandpass and notch it sets how narrow they are. Defaults to 0.7071.

Returns A new audio buffer.