I don't know if this has come up before, but some of the musicians associated with Bruton held a concert on March 29, 1980, and some of the show was actually recorded. The results were pressed in a very limited edition, labelled
The Bruton Concert, listed as BRZ 1, and given to the participants, but never released commercially. Here are a couple of examples, posted to YouTube by George Fields.
He seems to have posted the whole album. If you watch them on YouTube you can look at the accompanying notes and see the musicians involved.