“This is not my usual show,” said Hummel, a harp-playing bandleader who has played Bluesdays more than anyone with the exception of Chris Cain. “It will be along the lines of my earliest musical inspirations and people I saw in the very beginning. More of the history of the rock-blues stuff in relation to the old-style blues.

“We’re really representing what Bill Graham put out there in the San Francisco scene. What happened at his venue and Chet Helms’ venue, the Avalon Ballroom. Those two guys really created something in the music world in the ‘60s that was pretty unsurpassed. There wouldn’t be blues if it wasn’t for those two guys.

“Bill Graham was brave enough to put all these rock bands up with all these old blues guys. That’s where you had the melding of blues and rock together.”

 Helms was known as the father of San Francisco’s 1967 “Summer of Love,” and for recruiting Janis Joplin to join Big Brother and the Holding Company. Hummel will be accompanied by guitarist Gary Vogensen, who was mentored by Mike Bloomfield, the famed guitarist from the Paul Butterfield Blues Band and the vanguard of the Chicago-to-San Francisco migration of musicians in the late 1960s.