WATCH: Paul Simon sings 'Bridge Over Troubled Water' for divided Democrats

PHILADELPHIA, USA – Folk rock legend Paul Simon offered a badly needed message of unity to divided Democrats on Monday as he sang "Bridge Over Troubled Water" to their convention.

The singer's choice of song was especially poignant as the convention in Philadelphia was visibly divided between supporters of presumptive nominee Hillary Clinton and her leftist challenger Bernie Sanders.

Released in 1970 by his former duo Simon and Garfunkel, "Bridge Over Troubled Water" speaks of unity during tough times.

The choice of Simon as Monday night's entertainment added resonance as Sanders had embraced the Simon and Garfunkel song "America" for a campaign commercial.

Minutes after comedian Sarah Silverman denounced Sanders supporters who still resisted Clinton as "ridiculous," Simon had the crowd holding hands and singing together.

Whatever the message of unity, Simon's voice appeared to lose power and veer off-key as the song progressed. And he did not manage one gesture that might have reinforced his theme – he was not joined by former bandmate Art Garfunkel.

Simon, 74, had hinted that a concert last month in his native New York may have been his final show, although he also recently released a 13th solo album full of in-studio experimentation.

Simon was one of several acts to play on the convention's opening day following pop singer Demi Lovato and R&B chart-toppers Boyz II Men, who performed their single "MotownPhilly" in tribute to their hometown and the convention's host city.

Some of the biggest names in pop music including Katy Perry – who has more Twitter followers than anyone else – and Lady Gaga are also planning to play in and around the convention.

The performances come in stark contrast to the previous week's Republican convention which had few famous entertainers despite billionaire nominee Donald Trump's boast that he would bring some showbiz pizzazz.

In the end, the Republican convention and surrounding events drew right-leaning artists including Southern rockers Lynyrd Skynyrd and rock singer Kid Rock. –