function updateDescription() {
  if (soundFile.isPaused()) {
    description = 'Paused...';
    p.html(description);
  }
  else if (soundFile.isPlaying()){
    description = 'Playing! Press any key to pause';
    p.html(description);
  }
  else {
    for (var i = 0; i < frameCount%3; i++ ) {
      // add periods to loading to create a fun loading bar effect
      if (frameCount%4 == 0){
        description += '.';
      }
      if (frameCount%25 == 0) {
        description = 'loading';
      }
    }
    p.html(description);
  }
}
Analyze the sound.
Return array of frequency volumes, from lowest to highest frequencies.