I dunno mate,
I do know that a few years back the groups used to encode the audio in mp3 for games. You would then run a program that would decompress all the tracks into PCM as what the game would use...
A game called Anno 1602 did this, it was about 50MB and then nearer 400mb when decompressed.
But I don't download that sort of thing anymore
...few years older and richer so....
I wouldn't bother trying any of that anyway since its a lossy format + its only for pcm audio, all stuff these days is already compressed...
You could try a program called "7-Zip" it attains the highest compression ratios (better than ACE\RAR\ZIP\etc). Its CPU heavy but you won't find a better program, + its free
