particles.js

// A simple Particle class
window.Particle = function(position, acceleration) {
  this.acceleration = createVector(0, acceleration || 0.15);
  this.velocity = createVector(random(-1, 1), random(-1, 0));
  this.position = position.copy();
  this.lifespan = 255.0;
};

Particle.prototype.run = function() {
  this.update();
  this.display();
};

// Method to update position
Particle.prototype.update = function(){
  this.velocity.add(this.acceleration);
  this.position.add(this.velocity);
  this.lifespan -= 2;
};

// Method to display
Particle.prototype.display = function() {
  stroke(200, this.lifespan);
  strokeWeight(2);
  fill(127, this.lifespan);
  ellipse(this.position.x, this.position.y, 12, 12);
};

// Is the particle still useful?
Particle.prototype.isDead = function(){
  if (this.lifespan < 0) {
   return true;
  } else {
   return false;
  }
};

window.ParticleSystem = function() {
  this.particles = [];
};

ParticleSystem.prototype.addParticle = function(acceleration) {
  var x = random(0, windowWidth)
  var y = random(0, windowHeight)
  var position = createVector(x, y)

  this.particles.push(new Particle(position, acceleration));
};

ParticleSystem.prototype.run = function() {
  for (var i = this.particles.length-1; i >= 0; i--) {
    var p = this.particles[i];
    p.run();
    if (p.isDead()) {
      this.particles.splice(i, 1);
    }
  }
};

sketch.js

//ruby -run -e httpd . -p 5000
//cd ~/desktop/github/play_remix

function preload() {
  bass = {
    sound: loadSound('/audio/BASS.ogg'),
    playing: false,
    play: function() {
      this.sound.play();
      this.playing = true;
    }

  };

  breaks = {
    sound: loadSound('/audio/BREAKS.ogg'),
    playing: false,
    play: function() {
      this.sound.play();
      this.playing = true;
    }
  };

  pad = {
    sound: loadSound('/audio/PAD.ogg'),
    playing: false,
    play: function() {
      this.sound.play();
      this.playing = true;
    }
  };
}

function setup() {
  createCanvas(windowWidth, windowHeight);
  padPlay = new p5.AudioIn();
  fftPad = new p5.FFT();
  fftPad.setInput(pad.sound);

  padAmplitude = new p5.Amplitude();
  padAmplitude.setInput(pad.sound)
  system = new ParticleSystem();
}

function mousePressed(){
  bass.play();
  breaks.play();
  pad.play();
}

function draw() {
  var drawPad = fftPad.analyze();

  var backgroundPad = padAmplitude.getLevel();
  var showBreaks = breaks.sound.getLevel();

  // H, S & B integer values
  colorMode(HSB);
  background(255, 105, backgroundPad*255);

  beginShape();

  for (var i = 0; i < drawPad.length; i++) {
    point(i, drawPad[i]);
  }

  endShape();

  if (showBreaks > 0.01) {
    system.addParticle();
  }

  system.run();
}