Speed method

webaudio-example-6.js

speed(speed = 1) {
  // Ramp up faster when increasing speed, slower if decreasing
  const duration = (speed > 1) ? durationRamp.up : durationRamp.down;

  for (let i = 0; i < this.trackCount; i++) {
    this.sources[`source${i}`].playbackRate.exponentialRampToValueAtTime(
      speed,
      this.context.currentTime + duration
    );
  }
}