In Byzantine music most of the modes of the octoechos are based on the diatonic genus, apart from the "second mode (both authentic and plagal)" which is based on the chromatic genus. Byzantine music theory distinguishes between two tunings of the diatonic genus, the so-called "hard diatonic" on which the "third mode" and two of the "grave modes" are based, and the "soft diatonic" on which the "first mode (both authentic and plagal)" and the "fourth mode (both authentic and plagal)" are based. The hard tuning of the diatonic genus in Byzantine music may also be referred to as the "enharmonic genus"; an unfortunate name that persisted, since it can be confused with the ancient enharmonic genus.