The February 25, 2002 issue of PC Magazine offers a utility that displays a separate piano keyboard for each channel of a midi file, and "lights up" the keys used as the midi plays.
A separate "composite keyboard" at the top plays all of the channels together - similar to the keyboard display found in most notation programs.
The program runs on any Windows or NT (Win95,Win98,NT,Win2K, WinME, WinXP) platform.
For the "musician-user" the possible benefit would be the ability to "visualize" what is going on in each separate channel of a midi file. It can be really difficult, with complex (multi-channel) midis to figure out which channel(s) have the melody, which have the chords (which may be split across channels), and which are percussion and embellishments.
This program also lets you easily "mute" individual channels, so that you can listen individually to the ones you're trying to separate, and you can change the "instrument" that plays an individual channel to help you hear a particular part.
This program doesn't do much that you can't do with most MIDI editors, but may be much simpler for "non-technical" musicians to use to analyze a tune.
For the few of our people with an interest in such stuff, the C source code is included! The portions I've looked at seem to be well annotated, and one might expect it to be a good example of "clean code." The author, Charles Petzold, is well known, and I think has a very good reputation with programmers. Download from www.pcmag.com/utilities the file for MIDIColors. The file you will get is midiclrs.zip (363 KB). You will need WinZIP, or some other "unzipper" program to open it. Opening (unzipping) the .zip file gets you a setup.exe and a separate MIDI_src.zip. You don't need to do anything with the MIDI_src.zip if you're not interested in the "code," - although it does include a "help" file with a brief outline of MIDI pointers. Just run the setup.exe and you're in business.
For programmers - or the merely curious, I would suggest unzipping the MIDI_src.zip to a separate folder, since it contains about 30 files that you'll want to keep separated from the "run" files.