First of all, thanks for your comments! We were discussing this recently and it seems you were absolutely right, this theme doesn't really fit into a super hero hideout. The guys I'm working with had seemed to have something different in mind when talking about the music. While I'm still a big fan of more "natural" music, especially for the background of a hand drawn adventure game, it pretty much looks like we're going to have a bit more of electronic typed music for our game. Maybe there's some use for it in another project though...
@Kimbra Thank you very much! I used a sequencer (Cubase) and a combination of VST instruments (Piano, Drums) and soundfonts (Organ) for it. The guitar and bass are real, only passed through some quite clean amplification. I wish I could have used a real contrabass (altough I've never even touched one ;-), but due to the lack of several thousand bucks I sticked to an electric bass.