In several different medieval theories, a distinction was made between chromatic and diatonic semitones, as there were two different sizes of semitone in many tuning systems.
Marchetto of Padua, however, specified three types of semitone and called the third, naturally enough, the enharmonic; however, his names were matched with the intervals differently than in traditional theory.
(For a detailed examination, see Monzo, Speculations on Marchetto of Padua's "5th-tones".)
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