3. Harmony.—- When a modern person first hears a piece of accompanied plainsong sung, he is generally bewildered. The beginning may trouble him and the middle worry him—the ending invariably confounds him. The thing ends in no key recognised by the modern ear. In the old days there were no keys, but modes, each with its dominant, its tonic, and proper and appropriate ending. Until comparatively recent times musicians understood this quite well; to Purcell, and to composers much later than him, the old endings were perfectly satisfactory. This, for instance, left no sense of the unfinished:
Gradually two keys swamped and swept away the modes—our major and minor; then our modern feeling for key relationships was born. Here is the major scale of C with a satisfactory harmonic ending:
It will be noticed that the top note of the chord marked with a star, the last note but one of the scale, is a semitone below the last note of the scale and rises to the last note. That is a proper ending or full close; what was called a half-close was:
As a termination to a piece of music made up of the notes of the scale of C, and therefore said to be in the key of C, this was not satisfactory. To set the ear and the mind at ease, to get a feeling that the music has settled down on a secure resting-place, the first chord had to be repeated. And in these chords
lies the germ of the whole of the later music. Only two more steps were needed. By adding an F, or writing an F instead of the upper G in the middle chord, the chord of the dominant seventh was obtained:
