Ionian mode
Ionian mode is a musical mode or, in modern usage, a diatonic scale also called the major scale.
It is the name assigned by Heinrich Glarean in 1547 to his new authentic mode on C, which uses the diatonic octave species from C to the C an octave higher, divided at G into a fourth species of perfect fifth plus a third species of perfect fourth : C D E F G + G A B C. This octave species is essentially the same as the major mode of tonal music.
Church music had been explained by theorists as being organised in eight musical modes: the scales on D, E, F, and G in the "greater perfect system" of "musica recta", each with their authentic and plagal counterparts.
Glarean's twelfth mode was the plagal version of the Ionian mode, called Hypoionian, based on the same relative scale, but with the major third as its tenor, and having a melodic range from a perfect fourth below the tonic, to a perfect fifth above it.
