For some reason, I've noticed that certain themes songs won't be played anymore.
I've had the gremlin theme played in fire stratas were fire constructs where the main enemies, and some odd mashup of two songs played silently in a poison beast area.
Both the theme songs are still there in the sounds folder, but I've yet to hear them play since the recent patches. Am I the only one with this problem?
I think the changes were done to allow more variety in the music (i.e. the Construct theme only played in Deconstruction Zones, and only when it was theme-less.) Given that, now the themed themes don't play. I'd propose a pool for multiple tracks to have a chance to play on a level, if possible.
If that's already been implemented, then the other songs don't occur enough.
As for two tracks playing simultaneously, that's an occasional bug. It oft happens when you join a party in the middle of a battle room/arena, causing both battle music and level theme to audibly be heard.