All you need to play MIDI files is software that probably came with your computer: Media Player on Windows computers, and either QuickTime or iTunes on Macintosh machines.
The files on this site were transcribed by hand and probably contain errors. If you want to tell me about a mistake, or if you need help with the files, or even if you just want to say "howdy", you can reach me here.
Other good sources for choral MIDI files: