loop(startTime, rate, amp, loopStart, duration) {
    this._looping = true;
    this.play(startTime, rate, amp, loopStart, duration);
  }
Loop the p5.SoundFile. Accepts optional parameters to set the
playback rate, playback volume, loopStart, loopEnd.

@method loop
@for p5.SoundFile
@param {Number} [startTime] (optional) schedule event to occur
                            seconds from now
@param {Number} [rate]        (optional) playback rate
@param {Number} [amp]         (optional) playback volume
@param {Number} [cueLoopStart] (optional) startTime in seconds
@param {Number} [duration]  (optional) loop duration in seconds
@example
 <div><code>
 let soundFile;
 let loopStart = 0.5;
 let loopDuration = 0.2;
 function preload() {
   soundFormats('ogg', 'mp3');
   soundFile = loadSound('assets/Damscray_-_Dancing_Tiger_02.mp3');
 }
 function setup() {
   let cnv = createCanvas(100, 100);
   cnv.mousePressed(canvasPressed);
   background(220);
   text('tap to play, release to pause', 10, 20, width - 20);
 }
 function canvasPressed() {
   soundFile.loop();
   background(0, 200, 50);
 }
 function mouseReleased() {
   soundFile.pause();
   background(220);
 }
 </code>
 </div>