Yep, I used a sample library of classic Nokia bleeps made available in this Game Jam's discussion, and using that I made the monophonic music for the game as the Nokia 3310 could't play more than one kind of bleep at a time, or at least that was one of the Game Jam restrictions.
While I'm not sure exactly how faithful or not I've been to the Nokia's sound chip sound it was an interesting challenge to make background music with that restriction, and its going to be even more interesting (from a technical standpoint) to make sure the combat FX don't play over the music either!
Although I can definitely acknowledge my music-making skills themselves can use some work!