Singer Paul Simon performs "Bridge Over Troubled Water" during the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Jim Young

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mike Segar

Singer Paul Simon greets the audience while performing at the Democratic National Convention in Philadelphia, Pennsylvania, U.S., July 25, 2016. REUTERS/Jim Young

Singer Paul Simon greets the audience while performing at the Democratic National Convention in Philadelphia, Pennsylvania, U.S., July 25, 2016. REUTERS/Jim Young

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mike Segar

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S., July 25, 2016. REUTERS/Jim Young

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S., July 25, 2016. REUTERS/Jim Young

Singer Paul Simon acknowledges applause after performing at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mike Segar

Singer Paul Simon walks off stage after performing "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Lucy Nicholson

Singer Paul Simon bows after performing "Bridge Over Troubled Water" during the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Lucy Nicholson

Singer Paul Simon performs "Bridge Over Troubled Water" during the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Gary Cameron

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Gary Cameron

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Lucy Nicholson

Singer Paul Simon performs "Bridge Over Troubled Water" during the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Gary Cameron

Singer Paul Simon performs "Bridge Over Troubled Water" during the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Gary Cameron

Singer Paul Simon takes the stage at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Lucy Nicholson

Singer Paul Simon performs "Bridge Over Troubled Water" at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Gary Cameron

Singer Paul Simon sings during his sound check ahead of the 2016 Democratic National Convention in Philadelphia, Pennsylvania, July 24, 2016. REUTERS/Jim Young

Singer Paul Simon (L) and Jesse Jackson greet each other on the stage during Simon's sound check ahead of the 2016 Democratic National Convention in Philadelphia, Pennsylvania, July 24, 2016. REUTERS/Jim Young

British singer-songwriter and humanitarian Yusuf Islam (L), commonly known by his former stage name Cat Stevens, accepts his award after he was inducted during the 29th annual Rock and Roll Hall of Fame Induction Ceremony at the Barclays Center in Brooklyn, New York April 10, 2014. Singer Art Garfunkel (R) presented him with the award. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENTERTAINMENT)

Singer Art Garfunkel (L) hands British singer-songwriter and humanitarian Yusuf Islam, commonly known by his former stage name Cat Stevens, his award after he was inducted during 29th annual Rock and Roll Hall of Fame Induction Ceremony at the Barclays Center in Brooklyn, New York April 10, 2014. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENTERTAINMENT PROFILE)

Art Garfunkel waves after performing during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES)

Paul Simon (R) performs with Art Garfunkel during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT)

Paul Simon (R) waves with Art Garfunkel after their performance during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT)

Paul Simon (R) performs with Art Garfunkel during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT)

Paul Simon (R) performs with Art Garfunkel during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT)

Paul Simon (R) performs with Art Garfunkel during one of two 25th Anniversary Rock & Roll Hall of Fame concerts in New York October 29, 2009. REUTERS/Lucas Jackson (UNITED STATES ENTERTAINMENT)

Paul Simon (R) and Art Garfunkel perform at a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Art Garfunkel (L) acknowledges Paul Simon during a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Paul Simon (R) and Art Garfunkel perform at a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Paul Simon (R) and Art Garfunkel perform at a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Paul Simon (R) and Art Garfunkel acknowledge the crowd after singing "Bridge over Troubled Water" at a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Paul Simon (R) and Art Garfunkel embrace after singing "Bridge over Troubled Water" at a show celebrating the music of Paul Simon at the Warner Theater in Washington, May 23, 2007. Simon was awarded the inaugural Library of Congress Gershwin Prize for Popular Song. REUTERS/Jason Reed (UNITED STATES)

Musician Art Garfunkel sings "God Bless America" during the seventh inning stretch of the St Louis Cardinals versus the Philadelphia Phillies game on opening day in Philadelphia, Pennsylvania, April 3, 2006. REUTERS/Tim Shaffer

U.S. singers Simon and Garfunkel perform on stage during their free concert in front of Rome's ancient Colosseum. U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during their free concert in front of Rome's ancient Colosseum July 31st, 2004. The concert is the last date in the European leg of their Old Friends tour, marking duo's first appearance together in Italy and their first free concert since their free live performance at New York's Central Park in 1981. REUTERS/Alessia Pierdomenico

U.S. singers Simon and Garfunkel acknowledge the crowd at the start of their free concert in front of Rome's ancient Colosseum. U.S. folk rock musicians Paul Simon (R) and Art Garfunkel acknowledge the crowd's applause at the start of their free concert in front of Rome's ancient Colosseum July 31, 2004. The concert is the last date in the European leg of their Old Friends tour, marking duo's first appearance together in Italy and their first free concert since their free live performance at New York's Central Park in 1981. REUTERS/Alessia Pierdomenico

U.S. singers Simon and Garfunkel perform on stage during their free concert in front of Rome's ancient Colosseum. U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during their free concert in front of Rome's ancient Colisseum July 31st, 2004. The concert is the last date in the European leg of their Old Friends tour, marking duo's first appearance together in Italy and their first free concert since their free live performance at New York's Central Park in 1981. REUTERS/Alessia Pierdomenico

U.S. singers Simon and Garfunkel perform on stage during their free concert in front of Rome's ancient Colosseum. U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during their free concert in front of Rome's ancient Colosseum July 31, 2004. The concert is the last date in the European leg of their Old Friends tour, marking the duo's first appearance together in Italy and their first free concert since their free live performance at New York's Central Park in 1981. REUTERS/Alessia Pierdomenico

U.S. folk rock musicians Paul Simon (Centre R) and Art Garfunkel (Centre L) perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. [The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy.]

U.S. folk rock musician Paul Simon performs on stage alongside Art Garfunkel (not pictured) during an open-air concert at Hyde Park in London, July 15, 2004. [The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy.]

U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. [The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy.]

U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. [The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy.]

A character forming part of a fountain is lit up in Hyde Park in London as U.S. folk rock musicians Paul Simon and Art Garfunkel perform an open-air concert, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD

U.S. folk rock musicians Paul Simon (Centre R) and Art Garfunkel (Centre L) perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD/THI

U.S. folk rock musician Paul Simon performs on stage alongside Art Garfunkel (not pictured) during an open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD/THI

U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD/THI

U.S. folk rock musicians Paul Simon (R) and Art Garfunkel acknowledge the crowd's applause at the start of their open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD/DBP

U.S. folk rock musicians Paul Simon (R) and Art Garfunkel perform on stage during an open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham MD/DBP

U.S. folk rock musician Art Garfunkel performs on stage alongside Paul Simon (not pictured) during an open-air concert at Hyde Park in London, July 15, 2004. The concert is the second date in the European leg of their Old Friends tour, which will see the duo perform in France, Germany, Sweden, Denmark, Norway, The Netherlands and Italy. REUTERS/Matt Dunham REUTERS MD/THI

Recording and performing artists Paul Simon (R) and Art Garfunkel sing "Old Friends" during their concert in New York's Madison Square Garden, December 2, 2003. The duo are playing three sold-out concerts in New York, during their first tour in 20 years.

Recording and performing artists Paul Simon (R) and Art Garfunkel sing
"Old Friends" during their concert in New York's Madison Square Garden,
December 2, 2003. The duo are playing three sold-out concerts in New
York, during their first tour in 20 years. REUTERS/Jeff Christensen

JC

Recording and performing artists Paul Simon (R) and Art Garfunkel sing
during their concert in New York's Madison Square Garden, December 2, 2003.
The duo are playing three sold-out concerts in New York City during their
first concert tour in 20 years. REUTERS/Jeff Christensen PP03120007

JC

Recording and performing artists Paul Simon (R) and Art Garfunkel sing
"Old Friends" during their concert in New York's Madison Square Garden,
December 2, 2003. The duo are playing three sold-out concerts in New
York City during their first concert tour in 20 years. REUTERS/Jeff
Christensen

JC/GAC

Musicians Art Garfunkel (L) and Paul Simon (R) perform together during their "Old Friends Tour' October 18, 2003 at the Palace in Auburn Hills, Michigan. This is their first tour together in 20 years.

Paul Simon performs during the "Old Friends Tour' at the Palace in
Auburn Hills, Michigan, October 18, 2003. This is the first tour of
Paul Simon and Art Garfunkel in 20 years. REUTERS/Rebecca Cook

RC/GAC

Musicians Art Garfunkel (L) and Paul Simon (R) perform together during
their "Old Friends Tour' October 18, 2003 at the Palace in Auburn
Hills, Michigan. This is their first tour together in 20 years.
REUTERS/Rebecca Cook

RC/GAC

Paul Simon performs during the "Old Friends Tour' October 18, 2003 at
the Palace in Auburn Hills, Michigan. This is the first tour of Paul
Simon and Art Garfunkel in 20 years. REUTERS/Rebecca Cook

RC/GAC

Art Garfunkel (L) and Paul Simon perform together during their "Old
Friends Tour' at the Palace in Auburn Hills, Michigan October 18, 2003.
This is their fist tour together in 20 years. REUTERS/Rebecca Cook

RC

Musicians Art Garfunkel (L) and Paul Simon (R) perform a song during
the first concert on their current tour at the Arena in Wilkes Barre,
Pennsylvania, October 16, 2003. Simon and Garfunkel have made joint
appearances in the past but are touring again after breaking up several
decades ago. REUTERS/Tim Shaffer

TMS

Musicians Art Garfunkel (L) and Paul Simon (R) wave from the stage at
the start of the first concert on their current tour at the Arena in
Wilkes Barre, Pennsylvania, October 16, 2003. Simon and Garfunkel have
made joint appearances in the past but are touring again after breaking
up several decades ago. REUTERS/Tim Shaffer

TMS