function setup() {
  createCanvas(710, 256);
  fill(255, 40, 255);

  // loop the sound file
  soundFile.loop();

  filter = new p5.LowPass();

  // Disconnect soundFile from main output.
  // Then, connect it to the filter, so that we only hear the filtered sound
  soundFile.disconnect();
  soundFile.connect(filter);

  fft = new p5.FFT();

  // update description text
  p = createP(description);
  var p2 = createP('Draw the array returned by FFT.analyze( ). This represents the frequency spectrum, from lowest to highest frequencies.');
}
Example: Apply a p5.LowPass filter to a p5.SoundFile.
 Visualize the sound with FFT.
 Map mouseX to the the filter's cutoff frequency
 and mouseY to resonance/width of the a BandPass filter