But there is this fundamental difference, that, whereas our plainsong is strictly diatonic, and its intervals are constant, theirs is enharmonic, and has varying intervals. Not only do they sing 3/4 and 5/4 tones, but in different modes, even in the same mode, according as the melody rises or falls, the interval between two notes changes. As a specimen, this is the ascending scale of the first authentic mode, with the intervals between the notes in brackets: re (10/9), mi (16/15), fa (9/8), sol (10/9), la (9/8), si (16/15), do (9/8), re. When it descends the scale becomes: re (9/8), do (10/9), si (27/25), la (10/9), sol (9/8), fa (16/15), mi (10/9), re.^[1] On the other hand, in the second plagal mode, the interval re-mi is 16/15 tone, mi-fa, 600/503, &c. To Western ears this music certainly sounds very strange and barbarous. It is much discussed whether the enharmonic intervals are really Greek, or whether they are due to later Asiatic influence. The Byzantines have other musical practices that make their singing still more unpleasant to us. They add astonishing grace notes and incredible pneums, rushing through quarter-tones and half-quarter tones round about the note that we should expect them to hold. Their melodies continually change from one mode to another, and, as they have no accompaniment and only the vaguest pneums printed in their books,^[2] it is difficult for the singers to know what mode they should sing. To help them, a boy is made to sing the Ison (^{(Greek characters)}, dominant) continuously the whole time. As soon as the mode changes, the Ison-boy is made to suddenly raise or drop his note, and the whole choir knows that they must now sing in the new mode. If anything were wanted to make this amazing chanting still more unbearable to us, it would be the continual wail of the Ison-boy piercing through the apparently irresponsible vagaries of the choir. But the Western European who has heard what seems to be simply a confused shrieking with no rhythm, tune, nor method, should know that really their chant is the most wonderful display of accurate ear and skill in the world. Who of us could sing such intervals as 600/503 tones right, or at one flash, as the Ison-boy drops his doleful

1. ↑ Tables of all the modes, with their intervals, are given in E. d'Or., iii. pp. 213-215, L'harmonique chez les Grecs modernes.
2. ↑ They have never used our system of stave-lines.