gibberish-dsp/js/fx/tremolo.js

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

const g = require( 'genish.js' ),
      effect = require( './effect.js' )

module.exports = function( Gibberish ) {
 
const Tremolo = inputProps => {
  const props   = Object.assign( {}, Tremolo.defaults, effect.defaults, inputProps ),
        tremolo = Object.create( effect )
  
  let out
  tremolo.__createGraph = function() {
    let isStereo = false
    if( out === undefined ) {
      isStereo = typeof props.input.isStereo !== 'undefined' ? props.input.isStereo : false 
    }else{
      isStereo = out.input.isStereo
      out.isStereo = isStereo
    }    

    const input = g.in( 'input' ),
          inputGain = g.in( 'inputGain' ),
          frequency = g.in( 'frequency' ),
          amount = g.in( 'amount' )
    
    const leftInput = isStereo ? g.mul( input[0], inputGain ) : g.mul( input, inputGain )

    let osc
    if( props.shape === 'square' ) {
      osc = g.gt( g.phasor( frequency ), 0 )
    }else if( props.shape === 'saw' ) {
      osc = g.gtp( g.phasor( frequency ), 0 )
    }else{
      osc = g.cycle( frequency )
    }

    const mod = g.mul( osc, amount )
   
    const left = g.sub( leftInput, g.mul( leftInput, mod ) )

    if( isStereo === true ) {
      const rightInput = g.mul( input[1], inputGain ),
            right = g.mul( rightInput, mod )

      tremolo.graph = [ left, right ]
    }else{
      tremolo.graph = left
    }
  }
  
  tremolo.__createGraph()
  tremolo.__requiresRecompilation = [ 'input' ]

  out = Gibberish.factory( 
    tremolo,
    tremolo.graph,
    ['fx','tremolo'], 
    props 
  ) 
  return out 
}

Tremolo.defaults = {
  input:0,
  frequency:2,
  amount: 1, 
  shape:'sine'
}

return Tremolo

}