Making Pico Music in a fashion similar to Sonic PI

There are a number of examples on this site for creating musical sounds. Thank you for the help in creating this post.
When I bought a Raspberry Pi, I discovered the Sonic PI software that also runs on PC, Mac and Linux.
Program uses a modified Ruby interpreter.

Sonic PI

I wondered if something like Sonic Pi could be implemented using Espruino, at least a small subset.
Here is a first attempt:

//music.js
// 1 Nov 2017
// Tested on a Pico
// make music in a fashion similar to Sonic PI
// http://sonic-pi.net/
//
// Hardware
// Connect an amplified speaker input to ground and the Speaker pin
// as defined here
var Speaker=A5; //A9;
// use this to find a suitable pin
//analogWrite();
/*
Pico pins
Suitable pins are:
A0 A1 A2 A3 A5 A6 A7 A8 A9
A10 A11 A15 B0 B1 B3 B4 B5 B6
B7 B8 B9 B10 B13 B14 B15
=undefined

*/

var Tempo =1.0; // changes tempo of the music

// define some note lengths
var Whole=1.0;
var Half=Whole/2.0;
var Quart=Half/2.0;
var Eighth=Quart/2.0;

// Use this table to write the song as a seried of Midi notes,
// and durations
// http://www.electronics.dit.ie/staff/tscarff/Music_technology/midi/midi_note_numbers_for_octaves.htm

// Tune is C4 Major scale C4 is middle C, Midi note 60
var tune=[[60,Quart],
          [62,Eighth],
          [64,Quart],
          [65,Eighth],
          [null,Half], // a musical rest
          [67,Quart],
          [69,Eighth],
          [71,Quart],
          [72,Eighth]
          ];


var octave=Math.log(2);
var halftone=octave/12;

function freq(f) { 
  if (f===0) digitalWrite(Speaker,0);
  else analogWrite(Speaker, 0.5, { freq: f } );
}
function soundoff(){
  digitalWrite(Speaker,0);
}

function play(note){
  if(note===null)return; // a rest
note=note-60;
//console.log(note);
var tone=Math.exp(note*halftone);
//console.log(tone);
freq(261.63*tone); //C4 Middle C Midi note 60
}//end play



function wait(a,c){
var b=getTime();
if (b>=(a+c)) return b;
return a;
}

var a;
var b;
var i=0;
a=getTime();
//console.log(a);
setInterval(function () {
   //if(tune[i][0]!==null)
   play(tune[i][0]);
   b=wait(a,tune[i][1]*Tempo);
   if(b!=a){
    a=b;
    soundoff();
    i++;
   }
  if(i>=tune.length) clearInterval();
}, 10);

1 Attachment

• music.js