Mp3tag supports the following audio formats:
Advanced Audio Coding (aac)
Free Lossless Audio Codec (flac)
Monkey's Audio (ape)
Mpeg Layer 3 (mp3)
MPEG-4 (mp4 / m4a / m4b / iTunes compatible)
Musepack (mpc)
Ogg Vorbis (ogg)
OptimFROG (ofr)
OptimFROG DualStream (ofs)
Speex (spx)
Tom's Audio Kompressor (tak)
True Audio (tta)
Windows Media Audio (wma)
WavPack (wv)