The Aberdeen picture mentioned above reminded me of the line-up for the Humblebums' first major concert (and the "Merry Melodies" album launch. Billed as "The Humblebums and Friends" at the City Hall, Candleriggs, Glasgow. The "Friends" consisted of a galaxy of stars of the Scottish folk scene at the time (1969). Arthur Argo, editor of "Chapbook", then the only available journal of folk activities in Scotland, acted as compere and introduced most of the artists named above. Makes me wonder if the format was repeated in other locations. I saw the Humblebums a second time in the same venue, when they were joined by Gerry Rafferty, who seemed to me an incongruous addition. The main thing I recall about him was the painted front of his guitar, the work of "Patrick" (John Byrne).
Other people you might contact - Aly Bain occasionally did double-bookings with Billy Connolly. Also Fraser Bruce (on Facebook) has been seeking info re folk clubs and the early folk revival in Scotand with a view to a book.

Ross