piezo-test.js

var five = require("johnny-five"),
    board, servo, piezo;

board = new five.Board();

board.on("ready", function() {

  piezo = new five.Piezo(9);

  board.repl.inject({
    piezo: piezo
  });

  piezo.song("cdfda ag cdfdg gf ", "111111442111111442")

});

piezo.js

var Board = require("../lib/board.js"),
    events = require("events"),
    util = require("util");

function Piezo( opts ) {

  opts = Board.options( opts );

  // Hardware instance properties
  this.board = Board.mount( opts );
  this.firmata = this.board.firmata;
  this.mode = this.firmata.MODES.PWM;
  this.pin = opts.pin || 3;

  this.noteObject = {
    c: 262,
    d: 294,
    e: 330,
    f: 349,
    g: 392,
    a: 440,
    b: 494,
    C: 523
  };

  if ( !Board.Pin.isPWM(this.pin) ) {
    this.emit( "error", this.pin + "is not a valid PWM pin" );
  }

  // Set the pin to INPUT mode
  this.firmata.pinMode( this.pin, this.mode );

  // Piezo instance properties
  this.interval = null;

  this.playing = false;

  this.queue = [];

  // TODO: Implement a playback stack
}

util.inherits( Piezo, events.EventEmitter );

Piezo.prototype.tone = function( tone, duration ) {

  this.firmata.analogWrite( this.pin, tone );

  setTimeout(function() {
    this.firmata.analogWrite( this.pin, 0 );
  }.bind(this), duration );

  return this;
};

Piezo.prototype.song = function( tune, tempo ){
  
  var playTime = 400;
  var sequenceTime = 0;
  var self = this;
 
  var note, duration;
  for (var i = 0; i < tune.length; i+=1) {
    
    note = tune[i];
    duration = tempo[i];
    
    if (duration == '1') {
      duration = playTime / 4;
    }
    else if (duration == '2') {
      duration = playTime / 2;
    }
    else if (duration == '4') {
      duration = playTime;
    }
 
    if (note == " ") {
      self.firmata.analogWrite( self.pin, 0 );
      sequenceTime = sequenceTime + duration;
      console.log('break!');
    }
    else {
      console.log(tune, tempo);
 
      myNote = this.noteObject[note];
 
      (function (myNote, sequenceTime) {
        setTimeout(function () {
          self.firmata.analogWrite(self.pin, myNote);
          console.log('start' + myNote + ' - ' + sequenceTime);
        }, sequenceTime);
      }(myNote, sequenceTime));
 
      sequenceTime = sequenceTime + duration;
 
      (function (myNote, sequenceTime) {
        setTimeout(function () {
          self.firmata.analogWrite( self.pin, 0 );
            console.log('stop' + myNote + ' - ' + sequenceTime);
        }, sequenceTime);
      }(myNote, sequenceTime));
 
    }
  }
};

Piezo.prototype.fade = function( fromVol, toVol ) {
  // TODO: Add speed control
  toVol = toVol === 0 ? -1 : toVol;

  var now = fromVol,
      step = toVol < fromVol ? -1 : 1;

  this.interval = setInterval(function() {

    now = now + step;

    if ( now !== toVol ) {

      this.firmata.analogWrite( this.pin, now );
    } else {
      // this.firmata.analogWrite( this.pin, 0 );
      clearInterval( this.interval );
    }

  }.bind(this), 50 );

  return this;
};

Piezo.prototype.noTone = function(){
  this.firmata.analogWrite( this.pin, 0 );
}


// Piezo.prototype.alarm = function( pattern ) {

// };

// Piezo.prototype.note = function( note, duration ) {

//   var notes = {
//     "c": 1915,
//     "d": 1700,
//     "e": 1519,
//     "f": 1432,
//     "g": 1275,
//     "a": 1136,
//     "b": 1014,
//     "C": 956
//   };

//   return this;
// };

module.exports = Piezo;

cool, thanks for the help, going to play with this some more. going to see if adding accurate timing helps (https://gist.github.com/manast/1185904)

also saw that https://github.com/sparkfun/SIK-Guide-Code/blob/master/Circuit_11/Circuit_11.ino has a 10 millisecond pause after each note