So, I've had this issue with a few different games I've made.
Whenever I play a sound effect over the background music, it seems to lower the level of the music for the duration that the sound effect is playing. Like if I'm shooting a gun, the background music is quieter while the bullet noise is playing but it returns to normal volume once the bullet noise is over. I've found this happening whether I've imported the track as a sound or music.
Any thoughts? It's not a huge deal, but it's noticeable and I'd rather it weren't occurring.