I have music files from a DS Game I used to play when I was younger. They sound great, just the way I remember them. The only problem is that it still sounds like it was playing directly from a DS system. My favorite of the bunch (attached to this post) is the one I’m trying to practice on and make sound of good quality but to no avail. Is there anything I could do to fix the quality of the sound? Help is very much appreciated. 
The music was, at some time in its life, 11025 kHz sample rate. You can see that by the sharp cut-off in the spectrum at about 5500 Hz.Unless you have a better quality original to work from, there’s nothing that can be done to fix that. The high treble frequencies are not there and no amount of processing can put back what’s not there.
As the music is electronic may be acceptable to add harmonics : combining the original with a version pitch-shifted version one-octave-higher …