MAD is a high-quality MPEG audio decoder. It currently supports MPEG-1
as well as the MPEG-2 extension to Lower Sampling Frequencies. All
three audio layers (Layer I, Layer II, and Layer III a.k.a. MP3) are
fully implemented.

This is madplay (MP3-player) which is part of the project

WWW: http://mad.sourceforge.net/