Hypolydian mode

The Hypolydian mode, literally meaning 'below Lydian', is a musical mode or diatonic scale of ancient Greece that was based upon the Lydian tetrachord: descending (the way the Greeks always wrote about it), a series of falling intervals of a semitone followed by two whole tones. The rising scale for the octave is a single tone followed by two conjoint Lydian tetrachords. This is the same as playing all the white notes of a piano from F to F: F | G A B C | (C) D E F (ascending, in the modern reckoning). Confusingly, this scale in mediaeval and modern music theory came to be known as the Lydian mode.

The mediaeval music scholars, misunderstanding the Latin texts by Boethius of how the Greek modes were reckoned, used the term "Hypolydian" to describe the sixth mode of church music. This mode is the plagal counterpart of the authentic fifth mode, which Boethius dubbed "Lydian". The ecclesiastical Hypolydian mode is based on the relative scale of 'white notes' from F to F, with the musical dominant, the reciting note, or "tenor" at the major third on the scale (or A, in the F to F scale). The melodic range of the ecclesiastical Hypolydian mode ranges from the perfect fifth below the tonic to the perfect fifth above.