QUOTE(blackbelt @ Nov 19 2008, 10:46 AM)

how do I change the format to MP3? I downloaded some music and its .mid
You need to record playing midi files, then encode them to .mp3. Getting any sequencer program, and some DXi or VSTi to get good quality sound will be helpful. If you can't afford that, use midi player like SynthFont, and get good Soundfonts. It will make difference.