Drelbs was the best! It was the first game I can recall using an invisibility cheat to successfully play the game. The BASIC command was POKE 1337, 4200...or something like that.
Thanks Admiral. I've got some other C64 tunes in mind, but they are going to be quite a bit more involved than Drelbs. The Drelbs music is basically a 16 note pattern repeating.