The Rise of Tonality in the Seventeenth Century
According to Gioseffo Zarlino, the chief theorist of the sixteenth century, dissonance in music was tolerated because it made the subsequent consonances more beautiful and sweet by contrast. He advocated treating the dissonances in very special ways so that they would lose their sting and blend smoothly with consonances. For the most part composers were already doing just this. One might say that the general trend throughout the sixteenth century was to introduce dissonant notes in spots that were metrically unstressed. Suspensions, the more noticeable dissonances, had to be carefully prepared as consonances, held as dissonances for just one and not more than one beat, and then had to resolve down by stepwise motion to a consonance on the very next beat. The sacred music of Lassus, Palestrina, Victoria, and other, less famous composers is especially consistent in the strict manner in which they treated dissonance.