Hypodorian mode

The Hypodorian mode, a musical term literally meaning 'below Dorian', derives its name from a tonos or octave species of ancient Greece which, in its diatonic genus, is built from a tetrachord consisting (in rising direction) of a semitone followed by two whole tones.

The rising scale for the octave is a single tone followed by two conjoint tetrachords of this type.

Although this scale in medieval theory was employed in Dorian and Hypodorian, from the mid-sixteenth century and in modern music theory they came to be known as the Aeolian and Hypoaeolian modes.

[1] The term Hypodorian came to be used to describe the second mode of Western church music.

The ecclesiastical Hypodorian mode was defined in two ways: (1) as the diatonic octave species from A to A, divided at the mode final D and composed of a lower tetrachord of tone–semitone–tone, ending on D, plus a pentachord tone–semitone–tone–tone continuing from D, and (2) as a mode whose final was D and whose ambitus was G–B♭ (that is, with B♮ below the final and B♭ above it).