A family of muscle-specific transcription factors which bind to dna in control regions and thus regulate myogenesis. All members of this family contain a conserved helix-loop-helix motif which is homologous to the myc family proteins. These factors are only found in skeletal muscle. Members include the myod protein (myod protein); myogenin; myf-5, and myf-6 (also called MRF4 or herculin).