确定第三方应用程序正在iPhone上播放的歌曲

我正在尝试确定当前在iPhone上播放的歌曲的标题.我知道我可以使用以下代码来查找本地Apple应用程序正在播放音乐时正在播放的音乐，但是如果从Spotify或其他音乐播放应用程序中播放歌曲，如何查找歌曲的标题?

I am trying to determine the title of the song currently being played on an iPhone. I know I can use the following code to find out what is playing if the native Apple app is playing the music but how do I find the title of a song if its being played from Spotify or some other music playing app?

MPMediaItem *nowPlayingItem = [[MPMusicPlayerController iPodMusicPlayer] nowPlayingItem];
NSString *itemTitle = [nowPlayingItem valueForProperty:MPMediaItemPropertyTitle];