Don't you mean MP3? MPEG-4 is a video encoding standard ...
... though, to be fair, MP3 actually comes from an earlier MPEG standard, specifically, MPEG-1 Audio Layer 3!
Having said which, unless you music is monophonic (eg, a totally solo saxophone or somesuch), you're going to be stuck with using your ears to deconstruct it. No software yet exists that can "listen" to a musical ensemble and somehow dissect out the invididual parts.
The analogy which is frequently made, is that doing this would be a little like trying to create eggs, sugar and flour from a cake!