I make my own music on my Electric Keyboard & I bought an adapter to where it will go out of the headphones jack in my keyboard & hook into my computers Microphone jack. Then I just use the software that comes with windows for it afterwards, or you can download CDex which is a free program, that can record wavs longer waves than what comes in the multimedia toolbar thing with you computer & windows.
Just go do http://www.downloads.com & type in CDex, its free, can make wav files, can convert wav to mp3 (even though I wouldnt use an MP3 file in my game (requires a license so I hear to use in a comercial product.)
I hope that helps, CDex can do any wave editing, but I would also recomend turning your entire volume control things down almost all the way, otherwise youll have that staticy sound.