The Allman Brothers Band closed out the opening night of Eric Clapton's fourth Crossroads Guitar Festival on Friday (April 12) with a titanic six-song set, highlighted by 'Whipping Post.' Not to be outdone, Keith Richards of the Rolling Stones then dropped by for Saturday night's festival finale.

The two nights of the Crossroads Guitar Festival, lasting almost five hours apiece, benefited Clapton's Crossroads Center for substance abuse in Antigua. The festival has been held every three years since 2004. This was the first time the event has taken place at Madison Square Garden.

Richards joined Clapton for renditions of 'Key to the Highway' and 'Sweet Little Rock 'n' Roller' on Saturday night (April 13). Robbie Robertson of the Band also performed 'I Shall Be Released,' joining a star-packed list of festival performers that included Jeff Beck, Buddy Guy, John Mayer, B.B. King, Booker T. and the MGs, and others. On Friday, Clapton performed an acoustic set that featured 'Lay Down Sally,' 'Tears in Heaven' and 'Wonderful Tonight,' among other favorites.

The Allman Brothers' set included 'Statesboro Blues' and 'Why Does Love Got to Be So Sad?,' which found Clapton returning to the stage to reprise his role on the song from the classic Duane Allman collaboration 'Layla and Assorted Other Love Songs.'