Curious myself, I googled up a bunch of stuff on Amiga Disk Format, an old floppy filetype which obviously isn't what we're looking for. I did find out there is a program called VCRadio (not the more popular one which is shareware used in conjunction with PC radio cards), which will convert mp3 to adf... but not the other way around, I don't think - it's hard to tell, as everything I found on it is in French. I'm thinking maybe of turning on my recording feature and just playing the game, and then cutting out whatever comes before & after it on the recording... patchwork, but it beats nothing. I'll bump the thread with results if I get around to it. BTW you're talking about GTA Vice City?
Edit: got around to it sooner than I thought I would, it's as I suspected, sound quality leaves a bit to be desired, did my best - got a golf cart (no motor noise) & went into one of the middle Hyman Condos garages, but there's still noise from a passing car or two in the recording. Still beats nothing though.