message: stop the oscillator if it's started
diff: @@ -116,6 +116,9 @@ export class ToneOscillatorNode extends OneShotSource<ToneOscillatorNodeOptions>
  */
  dispose(): this {
  super.dispose();
  + if (this.state === "started") {
  + this.stop();
  + }
  this._oscillator.disconnect();
  this.frequency.dispose();
  this.detune.dispose();
  