I am not 100% sure if this is maybe a bug, but if an event with multiple mp3 files attached is triggered, it will always play the first mp3 file in the list for the event.

Is your feature request related to a problem? Please describe.
Because there is constantly a mp3 file that is playing I find it a bit annoying if always the same song starts playing if no special event is active (so basically just the generic event being active) or custom biome music is playing. To combat this problem I thought I could just add multiple mp3 files to the generic event. This resulted in the first song in the list being played everytime the event started (my expectation was that a random song from the list would be played). The big appeal in this mod for me is not only adding custom music but especially increasing the variety in the music. (I can't listen to minecraft music anymore because most of the time the same 5-6 song are played)

Describe the solution you'd like
My solution seems pretty simple although I don't know how much work it is for you. If you could just add the feature that if an event (or biome-"event") has multiple mp3 listed that a random mp from that list is chosen instead of starting with the first one that would be great! Maybe you could add a config to disable this if some people want the first song to play first always.

Describe alternatives you've considered
An alternative could be that everytime an event starts, the mod checks if it has been triggered in this play session before and what song was playing and then starting the next song in the list. But I think this would be harder to implement and for me personally it would not be better than random song selection.

So after some more testing on a fresh install with only ambience installed it does seem to randomize the songs. Not Sure if there is maybe some incompatibility with other mods I had installed for example dynamic surroundings or I just got really unlucky. Either way the mod works like I expected.

I do still have a suggestion though, which is not that important but could improve the experience. Shuffle mode in apps like spotify actually has some code behind it to make it less random, but seem more random. Not sure exactly how it works, but they basically prevent the same song from playing if it was already played a short while ago. Your could just make it so the mod doesn't play the same song twice in a row if the list contains more than 3 or 4 tracks (maybe this could be configurable?).