Simon and Garfunkel were influenced by the Everly Brothers

The siblings, who had hits with Wake Up Little Susie and Dream, performed a surprise set at a Simon and Garfunkel gig in Pennsylvania - and have agreed to join the whole tour.

Paul Simon paid tribute to the pair, saying he learned to sing as a duo by practising their harmonies.

Simon and Garfunkel are touring for the first time in 20 years, winding up in Tampa, Florida on 21 December.

The pair played their first gig on Thursday at the Wachovia arena in Pennsylvania.

The duo moved on to the Palace of Auburn Hills arena just outside Detroit, Michigan on Saturday, where they performed many of their best-loved numbers including Mrs Robinson, Homeward Bound and Sounds of Silence.

The pair have rarely appeared together in recent years

"We're thrilled to be here. This is a long time coming," said Garfunkel.

Paul Simon and Art Garfunkel went their separate ways after their 1970 album Bridge Over Troubled Water, but have performed together occasionally since.

The pair have a history of strained relations but reunited for a US arena tour in 1983 and played 21 sell-out dates in New York 10 years later.