How to prevent caching of music in Gingerbread?
Very unlikely. That's the MediaScanner's responsibility. For faster access it scans all directories on given events (e.g. SDCard mounted, boot_completed) and stores the results in a database, where most players pick it up from.

So you can either use a tool like e.g. SDrescan to trigger the MediaPlayer's scan whenever you've manipulated files -- or find yourself a music player that doesn't use Android's media database but rather works e.g. folder based.