The musical Baroque era spanned c. 1600 to 1750. During that era, composers were expected to keep one mood one emotion through a piece of music. You'll also hear steady rhythms, making it easy to tap along to the sounds.
Baroque composers followed these philosophies, put forth in the Doctrine of Affections. Music was indeed emotional, but composers were expected to keep a consistent affect through each movement or piece.
Toward the middle of the 18th century, a small group of composers working for Frederick the Great rebelled against the Doctrine.
Rather than sticking with one mood through a movement or piece, composers started shaking things up by inserting lots of pauses and frequently changing the mood of the music.
Carl Philipp Emanuel Bach, Johann Sebastian's second son (to survive), was a part of this movement, called Empfindsamkeit or "sensitivity".
Other composers included Johann Quantz and Jiri Benda, as well as JS Bach's oldest son, Wilhelm Friedemann Bach.
On today's Learning to Listen, hear examples of Empfindsamkeit along with samples of the music that came before it.