Fans who showed up early Friday afternoon at the Tumble Down concert featuring Vermont jam band Twiddle received a special treat – a guest appearance from Grateful Dead member Phil Lesh.

His son, Grahame Lesh, leads the band Midnight North. His group was the second act to play Friday at Tumble Down, Twiddle’s two-day mini-festival within the four-day Lake Champlain Maritime Festival at Waterfront Park.

The elder Lesh joined his son’s band about midway through its hour-long set that started at 4:15 p.m. He came out to loud cheers from the smattering of fans who arrived early for a concert scheduled to run until the conclusion of Twiddle’s second set at 11 p.m. Friday. The Grateful Dead co-founder acknowledged the crowd’s cheers with a bow of his head and his hand to his heart.

Phil Lesh sat in on guitar for four songs with Midnight North, including a cover of Jimmy Cliff’s “The Harder They Come,” sung from the stage by Mihali Savoulidis. He’s the guitarist for Twiddle, the improvisational-rock band that formed at Castleton University and hosts Tumble Down. Twiddle’s keyboard player, Ryan Dempsey, also sat in on Midnight North’s set.

Phil Lesh stayed through Midnight North’s final song, “Roamin’.” As Grahame Lesh thanked his father for joining the band’s set, Phil Lesh clasped his hands together in appreciation.

Tumble Down continues Saturday with another performance by Twiddle as well as sets by bands including Madaila, Lucid and Strange Machines. The Lake Champlain Maritime Festival ends Sunday with a concert by The Shins.

Contact Brent Hallenbeck at 660-1844 or bhallenbeck@freepressmedia.com. Follow Brent on Twitter atwww.twitter.com/BrentHallenbeck.