Red Rocks Amphitheatre played host to a great live music throwdown last weekend, as Trampled by Turtles, Elephant Revival and Shakey Graves joined forces at the historic Morrison, CO venue. Perhaps one of the biggest highlights of the night was the surprise guest appearance of Paul Hoffman and Dave Bruzza of Greensky Bluegrass, who joined TxT for a cover of Bruce Springsteen’s “Atlantic City”.The rock tunes is a staple of the Greensky catalog, and the two band members brought some great energy back to Red Rocks for the guest appearance. If you tilt your head sideways, you can watch this fan-shot video of the sit-in (or you can just listen!):Greensky Bluegrass was actually featured at Red Rocks the weekend prior, performing with Yonder Mountain String Band and Fruition at the national landmark. Check out our photos and recap from that show here.