As they announced earlier this week, Dead & Company will play a free show at The Fillmore in San Francisco this Monday, May 23. While preparing for the show, the group were joined by Van Halen rocker Sammy Hagar for a portion of the rehearsal, as bassist Oteil Burbridge showed via a video on his Facebook.

The clip shows Hagar fronting the Dead & Co guys on a blues tune while Bob Weir stands on the sidelines and watches, before Hagar eventually joins him and watches Burbridge and guitarist John Mayer rip through a solo section of the song. Watch the video below.

It remains to be seen if Hagar will join Dead & Company’s free show on Monday, but it wouldn’t be the first time the singer collaborated with the band. Earlier this year, Hagar joined Weir and Michael Franti for an acoustic set in San Francisco to support solar energy in California, and both Weir and drummer Mickey Hart also appeared on an episode of Hagar’s Rock & Roll Road Trip.

(h/t JamBase)