currentTime() {
    return this.reversed
      ? Math.abs(this._lastPos - this.buffer.length) / ac.sampleRate
      : this._lastPos / ac.sampleRate;
  }
Return the current position of the p5.SoundFile playhead, in seconds.
Time is relative to the normal buffer direction, so if `reverseBuffer`
has been called, currentTime will count backwards.

@method currentTime
@for p5.SoundFile
@return {Number}   currentTime of the soundFile in seconds.