Keith Richards made a surprise appearance at Madison Square Garden this weekend, joining Eric Clapton on stage to perform on Saturday night during the Crossroads Guitar Festival. Richards joined Clapton in playing “Key to the Highway” – a blues standard and Clapton favorite – and received what was likely the longest standing ovation of the two day festival.

Keith Richards’ appearance was only the beginning of Clapton’s hour-plus-long set, which also featured Robbie Robertson of The Band, among others.

“I just want to say it’s an honor to be here in honor of Crossroads and Eric Clapton,” Robertson told the crowd.

Crossroads Guitar Festival, which benefits Clapton’s Crossroads Centre for substance abuse in Antigua, has been held every three years since 2004; this Friday and Saturday was its first at Madison Square Garden.