This is a clip from a free jam I did with my friends at our secret studio (Voodoo Cookie Jamroom)
All the artists in the jam taught themselves how to play the instruments that they play. Most of us can't read or write in classical music notation, we just play by ear. We have a basic melody that we grow into elaborate rhythms for some of our material, but a lot of this is made up on the fly.
How do we communicate?
Well, sometimes I can hear someone change their beat or key and I adjust my own playing to harmonize. Sometimes I make eye contact, but honestly it's getting to the point where where all the senses and changes happen so quickly, it's almost as if everything is done through a 6th sense of cognitive communication.
it's another miracle of human evolution, people just need to learn to tap it.