LINKS AND DOWNLOADS
Audacity is a free audio editor. I use this for making simple cuts, volume adjustments, noise gates, etc. for sound files. There are lots of built-in effects — even pitch shifting! With the LAME encoder you can export to mp3 and it exports wav files natively. It’s a lightweight free program with an easy to use interface – perfect for slapping things together quickly.
Tip: If Game Maker wont play your mp3 for some reason, try exporting it through Audacity first to strip away whatever weirdness is going on with your file.