Remember back in June when legendary Grateful Dead guitarist Bob Weir joined the Avett Brothers onstage at Mountain Jam? Well, that kind of magic doesn't just happen. Sometimes it takes a solid five minutes of rehearsing to work things out.

Want proof? The Upstate New York music festival just released a really cool behind-the-scenes video (which you can watch above) of Weir and the band rehearsing 'Go to Sleep.'

We also caught up with the Avett Brothers at Mountain Jam to talk about how they were influenced by the Grateful Dead among other topics. Check it out: