My most memorable 4 were:

Ewan MacColl & Peggy Seeger a few times but best of all was at a house concert in LA, I just happened to drive in to LA from the East Coast that same day & was searching about town for music.

The Copper Family in Boston staged as a small local pub sing

The Watersons any number of times in any shape, way or lineup

But mostly what stands out as an all/one time wonder was Peter Belamy, solo at the Eisteddfod Festival held in southern Mass back sometime in the 70's I believe. I can still see him in my mind, bright flaming red suit, all over the stage, singing "On Board A Man O' War" & his Transport song "Walk Around Me Brave Boys & Roll Down" & I can still hear his straight high harmony on the chorus of "Roll Down" while the crowd sang the melody,,,,,,"RoOoLlLlLlL DoOoWwWwNnNnNn".

As a late teen in the 60's watching/hearing John Lee Hooker & his
fingers playing on the neck of his guitar, Dave Van Ronk in a gothic basement of a church drinking wine & singing of the devil & Big Mama Thorten singing at the Boston Tea Party (a club) & cursing Elvis for stealing her "HoundDog" & not having enough soul to sing it, after hearing her sing it she was right on the money too.
Life's been good to me.

Barry