Jack White made a surprise appearance at a Beck concert in Providence, Rhode Island on Saturday (26.07.14).

After headlining the Newport Folk Festival the same night, Jack rushed over to Providence to play acoustic guitar and sing backing vocals for tracks 'Pay No Mind' and 'Loser' during the encore.

The former White Stripes star was introduced simply as the ''best bartender in the world,'' according to Billboard.

Beck and Jack were later joined by Sean Lennon - who opened for Beck earlier in the night - as they performed a medley of 'Where It's At' and 'One Foot in the Grave.'

Fans were also thrilled as Jack performed a guitar solo and took part in a choreographed dance sequence.

Jack previously revealed he is a ''workaholic'' who can't deal with being ''idle'' and gets up at 6am every morning.

Jack - who has children Scarlet, eight, and Henry, six, with ex-wife Karen Elson - said: ''Some days I'll take the kids to school, and when I'm not on tour I'll be here. There's always a lot to do. A friend said recently, 'You're like me, a workaholic'. It's hard for me to talk about it because I might accidentally sound like I'm trying to fulfil some childhood guilt trip my father gave me, but it's not so much about work as a constant need to create something. If I'm idle, I don't think I deserve the right to be called an artist or a musician.''