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Jack Johnson just released a new single last week, but he treated festival-goers at Bonnaroo to something even newer than that this weekend.  Halfway through his headlining set Saturday night, Johnson told the crowd he had just written a new song that morning. 

The impromptu track told the story of being asked to fill in for Mumford & Sons at the last minute after the British folk-rockers were forced to cancel their appearance while bassist Ted Dwane recovers from emergency surgery.  Johnson summed up the hectic 48-hours before his performance with a chorus of "Oh, what the hell - it's Bonnaroo!"  He also dedicated his entire set to Dwane, and led a sing-along version of the Mumfords' Grammy-nominated hit "The Cave." 

Meanwhile, this year's Bonnaroo also featured performances from Paul McCartney, Björk, Haim, Passion Pitt, Of Monsters and Men, and many more. 

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