Watch John Mayer Cover The Grateful Dead In Chicago

John Mayer was in town this week performing two shows at the United Center and opted to keep his Dead & Company chops fresh during his stay.

Mayer busted out a cover of the Grateful Dead's "Fire On The Mountain" to the roaring delight of the crowd. It wasn't the only cover of the evening as Mayer performed songs by Pete Townshend, Beyonce, and Prince.

Just a day later, Mayer once again dipped into the Grateful Dead universe performing a cover of Jerry Garcia's "Deal".

Check out fan-shot video of the performance above.