The aesthetic basis of baroque music, from Monteverdi to J. S. Bach, was greatly influenced by a concept called the doctrine of affections.
In fourth century BCE, the philosopher Aristotle wrote a treatise entitled Rhetoric. In this work, Aristotle stated that the role of an orator is change the mind of their audience. In order to do this, they had to change the emotion, the affection, the passion within their listener’s mind. He said that you could do that be using what he called rhetorical figures. In other words, using the right words, in the right tone, at the right time, in just the right rhythm can move an audience from one emotion to another.
Music Theorists of the late 16th century began to see the parallels between these concepts of rhetoric and the practice of writing and performing music. They stated that the principle objective of music is to arouse an emotional state from the listener.
A group of Florentine nobleman, scientists, poets and musicians started gathering in 1576, calling themselves the Camerata Fiorentina. They championed this doctrine of affections calling for music to move away from the polyphony of the pervious few centuries in favor of monody. This term defines a style of music or song where one voice is featured while the rest of the voices or instruments play accompaniment to this principle line. The Camerata Fiorentina believed that this simplified form could better adhere to the rules of rhetoric and therefore better express emotions, passions, affections.
It is this turn to monody, a principle melody with accompaniment, that makes the music of the baroque stand in contrast to the music of the renaissance. Gone are intricate vocal lines of Palestrina and in their place stands the recitative of Monetverdi’s operas.
The doctrine of affections also meant that most compositions expressed only one emotion at a time. A piece was either joyful or full of sadness, expressing love or hate not a mixture of these passions.