getUrl() {
    // TODO: throw error if mp3 is not ready
    return this.mp3.url;
  }
Link to the mp3.
It can be used as a audio "src" value

@example
  microm.getUrl();
  // Something like --> "blob:http%3A//localhost%3A8090/8b40fc63-8bb7-42e3-9622-9dcc59e5df8f"
  
@return {String}