If you use baseplate that fires a projectile, say a bullet, down, and you have an entire grid of 1x1 bricks underneath this plate, I would give about a bricks worth of room just for the sake of it, and then have onProjectileHit -> NamedBrick (Music Bricks) -> PlayMusic on each of the bricks below the plate, that is a nice randomizer. You could also raise the chance of songs by making different sized bricks. For example, you could have a 4x4 brick and it would have 16 chances instead of 1.