One of the things I think LucasArts got Sierra beat in with regards to their old point-and-click adventure games has to be the music. I don’t mean that the music itself is better, but the underlying technology.
In SCI, a given music track can have cue points and a loop. These cue points can increase or set a value visible to the game engine, and let the game time things accordingly. Notable examples off the top of my head include the singalong text and images in Freddy Pharkas Frontier Pharmacist, the selection highlight following the beat in Quest For Glory, the singalong in Leisure Suit Larry 6… yeah.
But that’s just one way. The song can nudge the game, and that’s about it. A harmless bit of Mickey Mousing at best.
iMuse, on the other hand? The DirectMusic of its day. Remember DirectMusic? Me neither. Anyway, an iMuse song (near as I understand it) has queued triggers and a sense of beat, allowing the game to say “hey, switch to the cartographer’s version of Woodtick” and the song would wait for the current beat to finish, play a little flourish, and seamlessly transition into a different song. You could cancel them too, if you were fast enough. And let’s not get into the most triumphant example I’ve heard so far, X-Wing/Tie Fighter.
I figure if you give an SCI track beat markers, preload a fill riff, and have a script listen for requests, you might be able to approximate the basics. If you’re playing variations of the same song that only differ in instruments, you might be able to mute specific tracks, or send raw “Program Change” messages if you’re really adventurous…
But yeah. That’s why you can have proper MIDI dumps of SCI games, but you can’t quite hack it with most SCUMM games.