A gooey GUI
mpap allows you to play MPEG audio files on OpenStep/Mach 4.2 (Intel only; NeXT hardware isn't fast enough to decode mp3's in realtime). The most common use of this would be for playing "mp3" files, which proliferate wildly on the internet.
Important note: Back in 1999 and 2000, mpap was ported to run on pre-release versions of Mac OS X. That version is no longer being linked to here, since it does not work on any publicly-released version of Mac OS X, and is probably just confusing and disappointing to the dozens of people who continue to download it every month. Due to the fact that iTunes currently serves all my mp3 playback needs, mpap will not be updated any more in the future; However, its source is still kept here for educational purposes.