"How many bits?"

[AmigaSam]

Hi!

Is there an expert of old videogame music?

I love many of these old soundtracks, but I'm quite confused about their technical side.

Everybody knows that SNES and Mega Drive (Genesis) had a 16-bit sound system. NES was just 8-bit.
Despite being a 16-bit machine, Amiga also had 8-bit music (this was quite a surprise for me, since it sounded incredibly ahead of its time).

What about PC games? ("Doom", "Day of the Tentacle", "Command and Conquer", and so on...)

"The Secret of Monkey Island" is quite a mystery too. I know it was initially released on floppy disk, with 8-bit midi music ( https://www.youtube.com/watch?v=yMMIpp4HKRA ), but after two years it was released again on CD-ROM, with an improved sound ( https://www.youtube.com/watch?v=G7fRA_ep5Dw ).
Was this a 16-bit soundtrack or just an extremely efficient work on an 8-bit system (in the Amiga-style)?