The Scumm Bar claims the tracks are recorded from an MT-32. Somehow I doubt that.
I own an original Roland MT-32 and the Floppy-Version played with it sounds completely different. Especially the organs are very recognizable on the MT-32, those on the CD are not them.
Also the song at the cannibal village sounds nothing like MT-32 neither do those SFX in the ghost ship song.
I guess, those are recorded with stock synthesizers and wavetables at a Rainbow Arts studio, as they did the sound tracks for a few LEC games back then.
Well worth a mention is the fact, that the enhanced CD features several extended versions, which play longer than their MIDI-counterparts. And also there are some themes not present in other versions at all, as those are the ghost ship leaves Melee Island, at Stan's and at the cannibal village. Also there are two tracks, not used in the game at all, though they are nothing spectacular, as one is merely a slighly shorter version of the Lechuck Theme and the other are just very short one with few notes.
Also, the Scummbar claims that the Amiga version of Monkey Island 2 has better Musik than the PC version. This might be true compared to Adlib/Soundblaster, but in no way compared to a true MT-32.
Btw. The Amiga-Versions feature a combination of sampled MT-32 sounds and some from Yamaha wavetables. For example, the trombone in the Le Chuck-Theme is a very recognizable sound off the Yamaha PSS-Keyboards series.
I believe that is "music".