The baroque idea that only one feeling should be communicated in piece of music is known as

It's known as The Doctrine of the Affections.

The Doctrine of the Affections conveys that music has the capability to arouse a certain type of emotion among the people who heard it, which happened due to the combination of tempo, melody, and the lyrics that created by the artists.

The baroque idea that only a single feeling should be communicated in a musical piece is called homophony. Baroque represented a change in how music depends on words to convey the meaning of the musical piece. It is based on the theory that music should be a method to illustrate the words. Opera is a great example of music that was born in this time period.