I guess it does depend on what you call a circle. There are maybe a dozen of us in one. In the other there are probably three or four dozen. I don't know everyone. I got invited because I like genre bending. We've got a private forum where we share things.

Even outside of that, there is a place that used to be less private but has now gone private (guess why) where we would do Sunday songwriters. We'd get a topic, record a little something before the next Sunday, then share. After sharing we'd critique, do mashups, genre hop, create genre crossovers, and generally just have fun with each other's music.

I do not know how prevalent this is. I know of two private places, one of which is very small, and a third place that used to be public (with no expectation of anyone actually seeing it) but went private because of Suno.