In a preview of an upcoming concert at Red Rocks , guitarist Bob Weir of Grateful Dead/RatDog fame sat in with The Avett Brothers this afternoon at the Mountain Jam music festival in Hunter, NY.

The legendary Bob Weir takes the stage with the Avett Brothers. Pure cross-generational #MtnJamX magic. pic.twitter.com/j6ZIoAbKZ8 — Mountain Jam (@MountainJam) June 6, 2014

Weir and The Avett’s first-ever collaboration lasted for three songs and started six tunes into the band’s set. First up for the pairing was a cover of Jimmie Rodgers’ “California Blues,” which was followed by The Avett Brothers original “Go To Sleep.” Bobby ended his time on stage with the group by leading a cover of George Jones’ “The Race Is On,” a fitting choice considering the Belmont Stakes takes place tomorrow afternoon. “The Race Is On” was performed over 50 times by the Grateful Dead between 1974 and 1995.

Bob Weir shared a video from rehearsal on Facebook:

Ultimate Classic Rock has shared “The Race Is On” from The Avetts’ set:

Check out a photo Jay Blakesberg took during rehearsal:

We look forward to seeing what happens on July 11th, when the two acts team up at Red Rocks with Weir & RatDog set to open for The Avetts. Mountain Jam continues through Sunday. You can watch the action from home via a live webcast.