I misread: you said the music doesn't play continuously, not that it cracks. To track it down, Real C64 or emulator (which one)? PAL or NTSC?. Which download: the .d64, the Windows zip?
Thanks, that helped. You were right: sound effects (jumping, shooting, landing) were cutting out the drums and chords of the music, and the music wasn't recovering properly after each one. Version 1.1 is up with the fix, demo included. Would you give it another try?