Music converters convert songs and other music between popular formats like MP3, MP2, AAC, AC3, WAV, MID, MIDI, WMA, M4A, RA, RAM, OGG . There are many freeware and shareware programs available . Some of these are

audacity.sourceforge.net  – import a file and then export it in the desired format, open source software.

zamzar.com

jodix.com

www.tipard.com/all-music-converter.html – Tipard All Music Converter,  free trial available