The Spirit of Gregorian Chant - Church Music Association of America

42 THE SPIRIT OF GREGORIAN CHANT
the ordinary series of letters was called alphabet from the first two
Greek letters, alpha and beta. 1
The Greeks had a system of perfect concordance in the extremes
of their tetrachords, in the extremes of a fifth below, and in
the extremes of an octave below and of one above; thirds and sixths
were discords for the Greek ear. 2 The Church used for the con'
struction of her modal scales the ancient Greek tetrachords, the
intervals of whose intermediary notes comprised two whole steps
and one-half step in diatonic order, but did not take the enharmonic
or chromatic arrangement of the intermediary notes of the tetra'
chords, which the Greeks used for the sake of variety in default
of a fixed tonality. Certain variants between the Greek and the
Ecclesiastical Modes must, however, be mentioned, in that the
former started on E, moving downwards, while those of the Church
(ultimately established by medieval theorists) are thought upwards,
starting on D.
Among the Greeks, groups of notes were distinguished from
one another by pitch and grouping, and designated by tribal names,
which names the Church adopted, as well, and applied in her own
modal system, which is comparatively indifferent to pitch, but iden'
tified rather with a musical character called tonality.
Each of the Church Modes, eight in number, is composed of two
adjoining tetrachords, and has a determined tonality by reason of
the range of the notes in their sequence of steps and half'Steps, as
well as in their relation to two fixed points—the Dominant and the
Final. 3 A Gregorian melody moves in any one of these eight Modes,
which are the Dorian, Phrygian, Lydian and Mixolydian, called the
Authentic Modes, and the four Plagal Modes, which retain the name
of the Authentic from which each is derived but prefix it with
"Hypo." The fundamental tone of each Authentic Mode (the
Tonic), is the same in its Plagal or Hypo Mode, but the Dominant
of each in the same case is different. The ordinary Gregorian Chant
melody, with few exceptions, ends, in its whole as in many of its
1 Les MSI. Grig., Chap. III. * Ref., Grove's Diet., Greek Music. *Ref., Ibid, Modes, Ecclesiastic?!.