message: using exponentialApproachValueAtTime
diff: @@ -185,7 +185,7 @@ define(["Tone/core/Tone", "Tone/core/Buffer", "Tone/source/Source", "Tone/core/G
  if (this.curve === "linear"){
  this._gainNode.gain.linearRampToValueAtTime(this._gain, time + fadeInTime);
  } else {
  - this._gainNode.gain.setTargetAtTime(this._gain, time, this._gainNode.gain.getTimeConstant(fadeInTime));
  + this._gainNode.gain.exponentialAppraochValueAtTime(this._gain, time, fadeInTime);
  }
  } else {
  this._gainNode.gain.setValueAtTime(gain, time);
  @@ -268,7 +268,7 @@ define(["Tone/core/Tone", "Tone/core/Buffer", "Tone/source/Source", "Tone/core/G
  if (this.curve === "linear"){
  this._gainNode.gain.linearRampToValueAtTime(0, time);
  } else {
  - this._gainNode.gain.setTargetAtTime(0, startFade, this._gainNode.gain.getTimeConstant(fadeOutTime));
  + this._gainNode.gain.exponentialAppraochValueAtTime(0, startFade, fadeOutTime);
  }
  } else {
  this._gainNode.gain.setValueAtTime(0, time);
  