What is dynamics and music?

The 'dynamics' of music is the process of playing parts of the score or song louder
or softer, although, sadly, there's a lot of rock that doesn't do any of that.

In printed music ... the sheets that musicians use to play from ... the 'dynamics'
means the signs and symbols on the sheet that tell each instrument when to play
loud and when to play soft.  In formal music notation, there are actually symbols for
8 or 10 different levels of loudness, plus other symbols that tell the player when to
change, how fast to change, and how far to change.

Hey user  he  bachs contributions to the baroque period were bassed of keyed instruments