Three things were necessary before these Gregorian chants could develop at all: (1) A simple, clean-cut musical scale or systematized table of musical sounds. (2) Some definite manner of symbolizing sounds, so that they could be accurately expressed in writing. (3) A cultivation of the sense of hearing, in order that mankind might learn to distinguish between sounds that are discordant and those that sound well together; in other words, harmony. We will begin with the scale, and review what we know of the Greek modes in order to show how they were amalgamated into our present octave system of scales. [Tetrachords /------|-----\ /-------|--------\ ] [ F: b, c d e f g a G: b c' d' e' f' g' a'] [Mixolydian \--+-+-+-+-+-+----/ | | | | | | ] [Lydian \-+-+-+-+-+------/ | | | | | ] [Phrygian \-+-+-+-+---------/ | | | | ] [Dorian \-+-+-+------------/ | | | ] [Hypolydian \-+-+---------------/ | | ] [Hypophrygian \-+------------------/ | ] [Aeolian or Locrian or Hypodorian \---------------------/ ] [Notes labelled from highest to lowest: Nete, Paranete, Trite, Nete, Paranete, Trite, Paramese, Mese, Lichanos, Parhypate, Hypate, Lichanos, Parhypate, Hypate, [F: a,] Proslambanomenos.] Under Ambrose and Pope Gregory, these modes had taken a different form. The chromatic and enharmonic styles had been abandoned in theory, the portamento which the singers introduced into their chants being the only principle retained. The new system was as follows: [F8: g, a, b, G8: c d e f g a b c' d' e' f' g' a'] [First nine notes labelled: Hypoion., Hypodor., Hypophryg., Hypolyd./Ionian, Hypo-mixolyd./Dorian, Hypoaeol./Phryg., Lyd., Mixolyd., Aeol.] In order to complete the story of the evolution of scales and clefs, we must add that the Flemish monk, Hucbald (900 A.D.), divided this scale into regular tetrachords, beginning at G, with the succession, tone, semitone, tone, forming four disjunct tetrachords, [F: (g, a, b-, c) (d e f g) (a b c' d') G: (e' f+' g' a')] This division remained without influence on the development of the scale.