I\'m making Braid in Java. If you rewind the time, the sound plays backward.
How to play a WAV file backwards? Maybe with a stream with something like previous()
If the WAV contains PCM, reverse the order of the PCM samples. If it contains some other format it can be a lot more complex; probably easiest to just convert it to PCM first.
For more information on the WAV format, see this site.