// Based on example at https://processing.org/reference/libraries/sound/FFT.html
import processing.sound.*;

SoundFile song;
FFT fft;
int bands = 512;
float[] spectrum = new float[bands];
int scale = 20;

void setup() {
  size(512, 360);
  background(255);
  song = new SoundFile(this, "vibraphon.aiff");
  song.loop();
  fft = new FFT(this, bands);
  fft.input(song);
}      

void draw() { 
  background(255);
  fft.analyze(spectrum);
  for(int i = 0; i < bands; i++){
  // The result of the FFT is normalized
  // draw the line for frequency band i scaling it up to get more amplitude
    line( i, height, i, height - spectrum[i]*height*scale );
  } 
}