data-piano

Map numeric data to MIDI keyboard keys (where key 60 is Middle C)

Created primarily for use with baudio, but should work for other sound synthesis projects

Reference

Wikipedia article on piano key frequencies (note that this uses a standard 88-key piano rather than a MIDI keyboard)

Dominique Vandennucker's MIDI tutorial for programmers

Example

var DataPiano = require('data-piano')
var baudio = require('baudio')
 
var data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
 
var piano = new DataPiano({
    data: data, //Note data
    velocityData: data, //MIDI velocity data
    lowKey: 60, //C4
    highKey: 71, //B4
    lowVelocity: 42, //piano
    highVelocity: 80, //forte
    stopVelocity: 80 //Velocity sent with midi stop command, usually doesn't matter
  })
 
console.log(piano.keys) //[60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71]
console.log(piano.freqs) //Associated note frequency for each key
console.log(piano.velocities) //Associated velocity for each key
 
//Play two notes every second with baudio
var playFunc = piano.getSinPlayFunc(2)
var b = baudio(playFunc)
b.play()
 
//Get node-midi compatible "note on" message for the first beat
var firstBeat = piano.getMidiPlayFunc(0)(0)
console.log(firstBeat) //[144, 60, 42]

Defaults

{
  data: undefined, //Required
  velocityData: undefined, //Not required, defaults to generating constant velocity from averaging high and low
  lowKey: 60, //C4
  highKey: 71, //B4
  lowVelocity: 0,
  highVelocity: 127,
  stopVelocity: (lowVelocity+highVelocity)/2
}

API

var DataPiano = require('data-piano')

Main class for data-piano

DataPiano.keyToFreq(key)

DataPiano#keyToFreq(key)

Utility function that returns the corresponding frequency for a given piano key. Can be used as either a static or instance method.

DataPiano#getSinPlayFunc(bps)

Returns a function of time that represents the data played in sequence as sine waves, changing to the next key bps times per second

DataPiano#getSquarePlayFunc(bps)

Returns a function of time that represents the data played in sequence as square waves, changing to the next key bps times per second

DataPiano#getSawtoothPlayFunc(bps)

Returns a function of time that represents the data played in sequence as sawtooth waves, changing to the next key bps times per second

DataPiano#getMidiPlayFunc(channel)

Returns a function of beat # that represents the midi instruction to play the data in sequence, changing to the next key on each beat of the midi clock

DataPiano#getMidiStopFunc(channel)

Returns a function of beat # that represents the midi instruction to turn off the note from the previous beat, an instruction that must be passed every time you want to change to a new note

DataPiano#read/DataPiano#pipe

DataPiano instances are also readable streams, and will output a looping bytestream of midi messages that will turn on and off beat notes in sequence. It is up to the consumer to provide timing and midi port interfacing.