Indeed, it is not an exaggeration to say that all forms of instrumental music had to attend the definite shaping and establishment of the harmonic idea of music. This was a slow process, and nearly all instrumental music written before 1650, no matter how skillfully the thematic material is woven, lacks to our ears logical form, because of the vagueness or the monotony of its harmony. The system of harmony upon which our great instrumental music rests is so clear and familiar that it is hard for us to imagine another art of music in which it did not constitute a groundwork, in the structure of which, indeed, it held no firm place. Yet in the magnificent vocal music in the style of which Palestrina has left imperishable models, harmony, as we understand it today, did not enter. He and his great predecessors were guided seldom, it is easy to say they were guided not at all, by the beauties of chord progressions. They did not aim at modulations. Rather, by the rules of the art of their day, modulation was forbidden them. No composer might lead his music out of the _mode_ in which it began, to bewilder his hearer in a vague ecstasy of unrest, later to soothe him, gently shifting the harmonies back again home. Before his mind was the ideal of weaving many voice-parts, and to his pen the skill of countless imitations and independent melodies. The beauty of consonance after dissonance could not be appreciated by him, since to him each dissonance was a blemish. His was a music of flowing concord. Such harmonic discord as was inevitable was so smoothly prepared, so gently touched, that it now passes all but unobserved. This was essentially religious music. Many causes brought about the awakening of musicians to the beauty of harmony and its expressive power. The most effectual was the growing opera. The aim of the first writers of opera was the combination of dramatic recitation and music, from the union of which they shaped a style of music we now call _recitative_. The singing or reciting voice was accompanied by a few scattered chords upon the harpsichord, these chords serving at first mainly to mark cadences, later little by little to intensify the emotion of the play. It was then but a step to dramatic effects of harmony, to harsh, unprepared discords. The player at the harpsichord, always the nucleus about which the operatic orchestra grouped itself, began to appreciate chords as a power in music. The organist, under the influence of the dramatic style, thought of chords now and then in his slow-moving ricercars. The modes were broken down. A new system of scales, our own, grew up, which was adaptable to the new need of composers, to the sequence and contrast of chords. Harmony grew into music, became more than themes, than imitation and pursuit, the balance of its form.