Formation of the Greek Scale.—The Greek Scale was founded on a tetrachord or succession of four sounds, arranged as follows:
E (half tone) F (whole tone) G (whole tone) A
It is commonly believed that these letters written on the bass staff, thus:
represent the exact pitch, as near as may be, of this tetrachord. In early times the lyre was tuned to these four sounds, and was called the Tetrachordon; that is, four strings. This gracefully shaped instrument has remained to this day the symbol of music. This limited scale was extended by adding another tetrachord, which began with the last note of the first tetrachord, thus:
A—B♭ C D
E—F G A
making a scale of seven sounds, called the scale of Conjunct or Joined Tetrachords; also from its seven strings, the Heptachord scale. The next step was to take in the limit of the octave. The first way adopted was to raise the highest string a whole tone, thus making it the octave of the lowest; the sixth string was also raised a whole tone to make it a whole tone below the seventh. The result was a scale of seven sounds with one degree omitted, thus:
A—B♭ (C) D E
E—F G A
The next form was: