You are correct in noticing there is something weird about the number pad. There are a few keys missing, but you won't need them to pick the right answer. I took them out to make the answer less obvious when you first look at it, but to also make it very obvious once you realize where to find it.
The music doesn't relate to the lock you're currently working on.
The answer lies within the lock area of the safe, so keep your eye on that area.
Hope this hint drops you on the right path.