So much technical detail will be forgiven by the reader who can at all realize how profoundly the entire history of music has been affected by these acoustic and physiological facts. We have already seen how folk-music slowly wrought out the complex metrical forms based upon time grouping. In the same way, ecclesiastical music wrought out, slowly and laboriously, the harmonic and melodic forms that were based upon pitch-grouping. For a long time vocal utterance was defined only by certain simple intervals like the fall of the fourth, which formed the cadences of Greek dramatic recitation and of mediæval Christian intoning. Gradually ornamental notes were introduced as approaches to the final note; these were varied in pitch, and new ones added, until finally there resulted the ancient modes, precursors of our scale. Then, when two melodies began to be sung at once, the intervals of the octave, fifth, and fourth were again called into requisition, and made the bases of primitive harmony. In the old Organum of the Middle Ages, two voices, a fifth apart, gave the same melody, just as with the Greeks, in the process called «magadising,» two voices sang the same tune, an octave apart. So, step by step, pitch relations were perceived and utilized. In all stages of the long progress, whether the interval chosen was the octave or the fifth or the fourth, and whether the tones were sounded in succession as a melodic step or simultaneously as a chord, the guiding principle was the same; tones were grouped together which had pitch-form, which had partial tones in common and others not in common. A harmonic form, like a metrical form, was always a cluster of tones that could be both associated and distinguished.
It was a long time before these two means of organizing sound were used in combination. Until the seventeenth century metrical form was chiefly used, quite naturally, to define the gesticulatory part of musical material, the product of active emotion, while harmonic form gave coherence to the vocal part, the product of contemplative or religious emotion. Primitive dance either neglected pitch relationship entirely, as in that kind of savage music which uses only drums, tomtoms, clappers and such percussive instruments, or used only the simplest intervals like the fall of the fourth or the rise of the fifth. And in ecclesiastical Song, all through the Middle Ages, metrical regularity was not only not sought for--it was avoided. Even in the highly artistic song of the great choral epoch which culminated in Palestrina there was no rhythm. Phraseology depended entirely on the words. Composers avoided anything like an appearance of even sections, in sharp demarcation, balancing each other, such as we now demand. They liked rather to have their melodies cross and interlace like the strands in a basket, making a texture solid but inorganic. To them coherence was a matter merely of the individual voices; music held together like a rope rather than like a crystal. Indeed, any deeper harmonic unity was not feasible until they had gained more experience in tone relationship. But eventually the secular composers of the last half of the seventeenth century, among whom Arcangelo Corelli is a typical figure, learned to utilize both kinds of form, making them supplement and reinforce each other in all sorts of interesting and unexpected ways. With Corelli, pure music emerges as an independent art, beautiful as sculpture and promising new powers of expression. By his successors this new promise was realized with surprising rapidity. Constantly growing more independent of extraneous aids, developing, thanks to the fruitful interaction of metrical and harmonic grouping, an unprecedented richness and variety, music became in the hands of Bach and Beethoven a strong, flexible and efficient fabric, adapted to all phases of expression and capable of forming the most complex and self-sufficient structures. Evolved from the crude gestures and cries of naïve feeling by a never-ceasing, ever-widening exertion of man's intelligence, absolute music has become in some respects the most eloquent and penetrative of the arts.