By the beginning of the seventeenth century, moreover, there began to dawn upon men’s minds various new principles of musical construction which were pregnant with possibilities for a far wider and more vital development than any that had gone before. The rapidity with which the art now began to grow, ramify, and mature, the variety of the new tendencies, and the multiplicity of different styles or orders of art, such as opera and oratorio, fugue and sonata, toward which they led, are surprising. In the countless centuries before Palestrina music grew slowly and uniformly, like a plant; in the short three hundred years between the birth of Palestrina in 1528 and the death of Beethoven in 1827, it had its inconceivably rich and various blossoming, and Monteverde and Gluck, Corelli and Scarlatti, Couperin and Rameau, Bach and Handel, Haydn, Mozart, and Beethoven, were the bright flowers it now put forth. Such a rapid and many-sided advance is fairly bewildering; but it is nevertheless possible to distinguish in the movement a few salient and dominant features, more significant and remarkable than all the others. From our present point of view, the labors of J. S. Bach in the fugue and suite forms, and of Haydn, Mozart, and Beethoven in the sonata form, are of supreme interest. These labors were guided and fructified by several new principles of musical effect.[5] The first step toward new fields was taken early in the seventeenth century by a set of daring reformers in Florence, who, boldly discarding the perfect polyphonic style of Palestrina, contrived a style of dramatic music, embodied in small operas, in which single voices sing more or less expressive melodies over an instrumental accompaniment in chords. Crude in the extreme as were necessarily the compositions of Cavaliere, Caccini, Peri, and their fellows, they opened up novel paths, because they had to rely for their effectiveness largely on the conduct of the harmonies employed. So long as the old church modes were adhered to, to be sure, the harmonic style remained necessarily vague, wandering, and monotonous; but gradually the composers began to see that, by altering their intervals, they could introduce variety and contrast into their cadences, making one line end on one chord, and the next on a different though related one, and that thus they could make coherent the successive phrases, punctuated by the cadences, and at the same time set them in an opposition that made for variety. In the interests of definiteness of cadence and an obvious distribution of contrasted yet complementary chords, therefore, the modes were slowly transformed into the modern scale, and music became at last harmonically definite and firm. All the tones came to be conceived as grouped around certain tonal centres, which could be manipulated and organized like the masses in a picture. Thus emerged the principle of tonality or key, and in the course of time