Help me choose the right iPhone audio class - MPMoviePlayer vs AVAudioPlayer vs MPMusicPlayer

Does anyone know of a good tutorial on the difference between MPMoviePlayer and AVAudioPlayer vs MPMusicPlayer?

I want to play audio from an mp3 file accessible from an external url.

Ideally, it plays as iPod-like audio-audio. I've played around with MPMoviePlayer, but it seems to be more suitable for video, as when the sound starts, the message “playing movie” appears, the controls disappear and a white tooltip page appears.

I would like the standard ipod audio controls to show up all the time and adjust the image behind them.