Creating a drum machine

Now that you know how to analyze audio and visualize it, we'll take a look at how we can create instruments. We'll start with building a programmable drum machine with a 16-step sequencer, such as the famous TR-808 and TR-909 drum machines from Roland. You can find out everything about these classic drum machines at Vintage Synth Explorer, at http://www.vintagesynth.com/roland/808.php.

How to do it...

You can start by creating an empty sketch and saving it as drum_machine.pde. Add a new tab to the sketch and save it as Button.pde. We'll write a simple Button class so you can toggle buttons on and off. This class will also keep track of playing sounds.

class Button
{
  float x;
  float y;
  float w;
  float h;
    
  boolean isOn;
    
  Button( float _x, float _y )
  {
    x = _x;
    y = _y;
    w = 20;
    h = 20;
    
    isOn = false;
  }
  
  void render()
  {
    if ( isOn == true ) {
      fill( 255, 0, 0 );
    } else {
      fill( 255 );
    }
    rect( x, y...