You should be aware Dropbox seem to be having some hosting problems lately and sometimes fail to transmit files, which can break the project. It's a problem with Dropbox hosting rather than a C2 issue. It might work better if you use a real host (renting a cheap server is probably 10x better than Dropbox hosting).
C2 games work best with iOS 6+, and on Android definitely should be using Chrome for Android instead of the stock browser. PhoneGap is known to have awful performance on Android and iOS, which is why we recommend using CocoonJS instead. Also for a music-based app you probably need support for the Web Audio API for low-latency audio playback - currently this is only supported on Chrome desktop and Safari for iOS 6+. Firefox are working on support too.