But even after they are provided with perfected instruments, men are still much restricted in their search for lovely effects of tone unless they have also a well-developed tonal technique, or science of harmony. The tools are not enough; the use of them must also be known. As we have seen, however, the harmony of Palestrina and his school was for all its purity somewhat colorless and flat. A harmonic fabric made up exclusively of consonant chords is like a picture painted altogether with pure, light colors; it is wonderfully bright and transparent, but its very purity makes it lack force. For the sake of contrast an admixture of dissonances is required, much as shadow is required in a picture, or harshness and irregularity in a poem. The entirely sweet, soft, and mellifluous series of chords at first charms, but finally cloys. One of the important tasks of seventeenth century composers, therefore, was to find out how to introduce dissonances in such a way as to invigorate without disrupting the fabric. Their harshness must not be obtruded, but it must be used. The Florentine reformers and their successors showed great skill in solving the problem. They learned how to “prepare” a dissonance, that is, to let one of its constituent tones appear in a consonance and then hold over while other voices moved to dissonant intervals; they experimented in harsher and harsher dissonances, admitting them only with great circumspection, but using their characteristic qualities with striking effect; and they established, as cadences, conventional formulæ of chords containing dissonant intervals, which became by mere force of repetition acceptable and familiar. In this way they introduced into the material of music a variety and range of color that consonances alone could never give. “Monteverde,” says Mr. R. A. Streatfield, “with his orchestra of thirty-nine instruments--brass, wood and strings complete--his rich and brilliant harmony, sounding so strangely beautiful to ears accustomed only to the severity of the polyphonic school, and his delicious and affecting melodies, sometimes rising almost to the dignity of an Aria, must have seemed something more than human to the eager Venetians as they listened for the first time to music as rich in color as the gleaming marbles of the Cà d’Ora or the radiant canvases of Titian and Giorgione.” If we could disabuse our minds of all emotional and æsthetic perceptions while listening to modern music, we should still find it vastly superior to the choral art of the middle ages in its purely sensuous richness. Sensuously it is a kaleidoscope of shifting effects, now harsh, now sweet, now resonant and sibilant, the next moment infinitely wooing and grateful; and through all ever changing its outlines and melting from color to color like the iridescent film of a soap-bubble.