FolkieDave - does he wear another hat in another place, by the way - observes a swing to instruments.

My local session experienced this before my time. There was a song session on a Monday.Instrumentalists arrived, and came to dominate that. The singers changed to Wednesday. Instrumentalists moved into that too.Session is now elsewhere, and still has some song ; doesn't have Ed Rennie singing Dives and Lazarus any more.

It may be coincidence that a local fiddler lived a hundred yards away from the pub but didn't discover the session for twenty years....

Trying to think when I first heard - or at least noticed - a melodeon.
Went to various clubs in Surrey in the 60s - guitar predominated, perhaps an occasional concertina. Almost all song rather than played tunes. Probably in the mid-90s. Mr Rennie - then in his Post Office uniform and others. Cluster of uniformed postman in used to appear at the end of the shift and pull out squeeze-boxes.

Of course, in the 60s, it was clubs and I wouldn't have known where to find a session.