The original Greek scales, or modes, as they were called, were all constructed within the compass of a perfect fourth, the primary interval fixed by Pythagoras. Each mode consisted of four notes, corresponding to the original four strings of the lyre; and the difference between these modes lay in the arrangement of their intervals, since only the highest and lowest notes were always the same distance apart, and in the pitch of this perfect fourth within which they were comprised.
Modes were thought of as extending downward; and they were of three kinds, the diatonic, composed of tones and half-tones, the chromatic, of two half-tones plys an interval of a tone and a half, and the enharmonic, of two quarter tones plus an interval of two whole tones.
The diatonic modes were the most important, while the two other kinds were frowned upon by the purists; and each of the diatonic modes was supposed to possess distinctive attributes, such as the Dorian, manliness, and the Lydian, inspiration. The principal diatonic scales were seven in number, namely the Dorian, Phrygian, Lydian, Mixo-Lydian, Hypo-Dorian, Hypo-Phrygian, and Hypo-Lydian; and there were also combinations of tetrachords into the Lesser Perfect system, extending an octave and a half, and the Greater Perfect system, extending for two octaves.
For notation the Greeks used letters, places in different positions, to denote the pitch but not the character of sounds.