Hypolydian mode

[1] The name is taken from Ptolemy of Alexandria's term for one of his seven tonoi, or transposition keys.

The third above the final, A—corresponding to the reciting tone or "tenor" of the sixth psalm tone—was regarded as having an important melodic function in this mode.

The sequence of intervals was therefore divided by the final into a lower tetrachord of tone-tone-semitone, and an upper pentachord of tone-tone-tone-semitone.

However, from as early as the time of Hucbald the Hypolydian mode—even more than the corresponding authentic mode, the Lydian—was characterized by the predominance of B♭ instead of B♮ as the fourth degree above the final.

Finer distinctions among the scale degree are sometimes made, with the D below the final called the "mediant", the lowest note, C, the "participant" (a tone functioning as an auxiliary to the mediant), the G, B, and B♭ the "conceded modulations" (subsidiary degrees), and the lowest C, the final, F, and (rarely) the D the "absolute initials".