I noticed that playing a looped OGG file can severely cut my game's performance on the Pocket PC from the near 30fps to as low as 15fps! (Ouch!) I don't know if it's a default or forced setting, since I've never used OGG files before I started with Game Editor, but do they always have to be 44KHz? Does that make a performance difference, compared to a song rendered in 11KHz or 22KHz?
How about MOD, S3M, or XM files versus OGG files? Which takes more processing cycles/CPU time to decode and play these file types? Of course, I'm not looking for benchmark numbers, just a rough calculation or comparison of the different file types.
Bottom line is that I really would want to get a good soundtrack behind my game, but I'm afraid it may really impact it negatively in its performance.