I don’t really have any tips regarding theory, i never picked it up mostly due to laziness. Admittedly, i never felt the need as my lack of knowledge didn’t keep me from cutting records and touring. But your post cheered me up, and it made me want to point out the incredible satisfaction of sharing a musical moment with other people. Doesn’t have to be a band or a committed project. Just having another instinct leading the music in unexpected direction is a great way to learn new stuff. It’s not something you need to do to grow, music is its own person in some senses: even when you play alone it’s you AND music. But if you get the chance to play with someone: take it!