The Amiga is loaded with custom chips to handle sound and video. MOD files take advantage of the fact that the Paula chip supports 4 channels of DMA sound output.
A Mac Classic should be able to play simple digital audio like the system sounds. Some games played music, but it was usually just monotone beeps and boops (Wheel of Fortune on the Portable sounds like this). An 8Mhz 68000 just doesn't have the horsepower to do serious real-time mixing of multi-channel music.