I have to second this and I've noticed a few people say this in the forums. For me the music is much quieter than C:R which may not seem like an issue, particularly if you aren't a fan of the music.
To solve the issue I have had to up the music vol in the audio menu, drop the other FX sliders and then I have to increase the maximum volume in game and manually increase my headphone volume to get a decent balance.
Again, probably not an issue, however there is a short spike in music volume, on the race loading screen, literally just before the race starts, which literally blows my head off
Exactly the same here. Music is by far much quieter than all other sounds, except just as a level is finishing loading and doing that intro camera swoop, where it suddenly becomes really loud for about 1 second, maybe less. Never had this problem with Reincarnation, but have had this problem with Max Damage since I started playing it. Glad to see it is not just me.
Really hoping it will get patched because I actually really like the music.