MPC to MP3,MP2,WMA , WAV, OGG, APE, AAC(utilized by iTunes),FLAC(lossless compression),MP4,M4A, MPC(MusePack),AC3,TTA,ofr(OptimFROG),SPX(Speex),Ra(Actual audio), and WavePack. If you are exporting a relentless bit rate spoken word MP3 corresponding to an audiobook and have a stereo track in Audacity where each channels are an identical, it is preferable to make use of Tracks > Mix > Mix [...]