message: simplifying the add method
  doesn't need to test at both if statements assuming that the API is followed
diff: @@ -143,10 +143,10 @@ export class ToneAudioBuffers extends Tone {
  url: string | AudioBuffer | ToneAudioBuffer,
  callback: () => void = noOp,
  ): this {
  - if (url instanceof ToneAudioBuffer || isAudioBuffer(url)) {
  - this._buffers.set(name.toString(), new ToneAudioBuffer(url, callback));
  - } else if (isString(url)) {
  + if (isString(url)) {
  this._buffers.set(name.toString(), new ToneAudioBuffer(this.baseUrl + url, callback));
  + } else {
  + this._buffers.set(name.toString(), new ToneAudioBuffer(url, callback));
  }
  return this;
  }
  