audio file as input

I'm wondering how to use a .wav/mp3 file as an input, for example replacing the mouse input in this example: 

processing-2.0b7\modes\java\examples\Basics\Input\Mouse2D

I could work at 5 fps and sample the amplitude out of the file, left and right channels - I'm not sure what else would be easy to get if anything. Or offline render and use a much higher fps to more accurately track the rhythm of the music.

Thanks!