gibberish-dsp/js/instruments/cowbell.js

Gibberish is designed to be an optimized API for audio synthesis using per-sample techniques.

let g = require( 'genish.js' ),
    instrument = require( './instrument.js' )

module.exports = function( Gibberish ) {

  const Cowbell = argumentProps => {
    let cowbell = Object.create( instrument )
    
    const decay   = g.in( 'decay' ),
          gain    = g.in( 'gain' ),
          loudness = g.in( 'loudness' ),
          triggerLoudness = g.in( '__triggerLoudness' )

    const props = Object.assign( {}, Cowbell.defaults, argumentProps )

    const bpfCutoff = g.param( 'bpfc', 1000 ),
          s1 = Gibberish.oscillators.factory( 'square', 560 ),
          s2 = Gibberish.oscillators.factory( 'square', 845 ),
          eg = g.decay( g.mul( decay, g.gen.samplerate * 2 ), { initValue:0 }), 
          bpf = g.svf( g.add( s1,s2 ), bpfCutoff, 3, 2, false ),
          envBpf = g.mul( bpf, eg ),
          out = g.mul( envBpf, g.mul( gain, loudness, triggerLoudness ) )

    cowbell.env = eg 

    cowbell.isStereo = false

    cowbell = Gibberish.factory( cowbell, out, ['instruments', 'cowbell'], props  )
    
    return cowbell
  }
  
  Cowbell.defaults = {
    gain: 1,
    decay:.5,
    loudness:1,
    __triggerLoudness:1
  }

  return Cowbell

}