Wow. That's a shocking difference and it's similar to what I remember from back then. There was some truly wonderful music composed for these games which only a lucky few players got to hear. That video shows the similar MU50 which was a cost-reduced MU80 that could play 16 different voices at once with 32 track polyphony. The MU80 did 32 different voices at once with 64 track polyphony, although a game's soundtrack would need to use the extra voices to make a difference.

Most of the MU series were backward compatible with the newer ones mostly adding more voices, polyphony, samples, effects and expansion options. Thanks to MAME we don't have to choose as we can have them all including 1999's MU128 which could play 64 different voices at once with 128 track polyphony.