The Roland MT-32 not initially developed for the home computer game market. It was first developed as a synthesizer expansion unit for use by professional musicians. If your D-50 couldn't spit out enough simultaneous voices (synth polyphony), just add an MT-32 and let it take care of the some of the background stuff (that's where the “32” in the name came from, it could sound up to 32 voices simultaneously).
The MT-32 was a sleek looking unit for it's time. The front panel sported a volume knob, ten buttons and a small, green LCD screen used to indicate the current patch and to help facilitate patch programming.
At some point, someone figured out that this low cost (relatively speaking) unit was a good match up for computer games of the era and heavy marketing campaigns ensued.
Game sound designers made good use of the machine and took the MT-32 to it's limits. Some even went beyond sound entirely and used MIDI sysex commands to display messages on the MT-32's LCD screen.
Once the market for computer game sound hardware took off (to the extent that it did), Roland started to make synth modules that were designed specifically for the computer gaming market. The first such of these modules was the CM-32L (the “CM” stood for “Computer Music”, the “L” stood for Linear Arthmetic Synthesis, also known as “LA”).
Internally, the CM-32L contains everything that the MT-32 does, but contained an additional 33 samples in it's wave banks. Most of the added samples were sound effects. There are several games that make use of these added sound effects, such as Beneath a Steel Sky and Ultima Underworld. If you play these games with an MT-32, you will get the music, but you will miss out on a few sound effects here and there. This was designed in such a way that an MT-32 user would not know that they were missing anything but the CM-32L, CM-64, CM-500 user would be treated to a nice surprise with extra sounds.
Since the CM-32L was meant primarily for computer games, it lacked the buttons and LCD screen of the MT-32. The CM-32L only a single knob for volume, and two LEDs to indicate power and MIDI message status.
The sound output of the CM-32L was also a bit less noisy than that of the MT-32.
This unit was primarily made for use computer musicians rather than games. Where as the MT-32 is an LA synthesizer, the CM-32P is basically a simple PCM (hence the “P”) wave table synth. It was a computer music version of the Roland U-110 keyboard (actually, due to a slight redesign it was much more quiet than the U-110). Being that it was entirely PCM sample based, it is much less flexible than either the MT-32 or the CM-32L. Some Japanese computer games (Roland is a Japanese company after all) did make use of the CM-32P, but none that I know of in the US/EU market. There was a slot on the front panel to accept Roland PCM wave cards to expand the sample set. Supposedly, a very few Japanese games were made that made use of a specific PCM card when inserted into the 32P but this has never been verified.
At one point in time the CM-64 was the ultimate Roland game synth to own, but at a debut price of well over $1000 USD not many could afford it. The CM-64 is a CM-32L and a CM-32P combined into one box. It is fully MT-32 compatible. This unit will work just fine for MT-32 or CM-32L games, but few if any games were actually designed to utilize the CM-32P side at the same time as the CM-32L. The CM-64 has the same Roland PCM wave card slot on its front panel as the CM-32P.
The LAPC-I (Liner Arithmetic Personal Computer I, that's the letter "i" not the number one) was an ISA card that housed an MPU-401 MIDI interface along with a built-in CM-32L. This unit is fully compatible with both the MT-32 and the CM-32L. Basically, it's a CM-32L on an ISA card.
The MT-100 was never intended for the computer game market. It was basically a Roland MT-32 with a built in PR-100 MIDI sequencer. While it is fully backwards compatible with the MT-32, it holds no advantages over the MT-32 as far as computer gaming is concerned.