A long time ago, in another ethnos... Pro and semi-pro musicians would occasionally get together to bounce musical ideas off eaach other. THis was not a reehearsal...few of them played as a group elsewhere; it wasn't an "open jam"...simply because it wasn't open. It gave accomplished musicians a chance to expand musical horizons. And it's a practice that, IMO, is sorely missed.

By me, at least.