dominant, C; his Lydian corresponded to the old Hypolydian,
dominant, C; and his Mixolydian to the old Hypophrygian,
dominant, D. These modes were accepted by the church and were called the Authentic modes.
Almost two centuries later, Gregory the Great added four more modes, which were called Plagal or side modes (from plagios—oblique). These were as follows:
Hypodorian,
dominant, F.
Hypophrygian,
dominant, A.
Hypolydian,
dominant, A.
Hypo-mixolydian,
dominant, C.
It is easy to see that these so-called new modes are simply new versions of the first four; although they are lowered a fourth beneath the authentic modes (hence the hypo), the keynote remains the same in each instance. Still later two more modes were added to this list, the Ionic,
dominant, G, which corresponded to the ancient Greek Lydian; and the Æolian,