code: public SoundCloudTrack previous() {
          int tracks = mSoundCloudPlaylist.getTracks().size();
          mCurrentTrackIndex = (tracks + mCurrentTrackIndex - 1) % tracks;
          return mSoundCloudPlaylist.getTracks().get(mCurrentTrackIndex);
      }
docs: Retrieve the previous track.
  
  @return previous track to be played.