Paul Simon called for unity among those at the Democratic National Convention with his classic Simon & Garfunkel hit "Bridge Over Troubled Water." His appearance last night in Philadelphia was described as a "surprise" by Rolling Stone, who said he appeared "before a crowd still coming together after a fractious primary."

Simon & Garfunkel had earlier given Democratic candidate Bernie Sanders permission to use their song "America" in his challenge to eventual nominee Hillary Clinton. Simon's former partner Art Garfunkel had, in fact, called himself a "Bernie guy" during the primary season.

So there was great symbolism to Simon's appearance, something acknowledged by earlier speakers Al Franken and Sarah Silverman, who represented both sides of the Democratic primary fight.

“You know, Sarah, what I love about us both being here is that we’re like a bridge,” Franken said, according to Entertainment Weekly. “How do you, figure that, Al?” Silverman shot back. “Well, you were for Bernie; I’m for Hillary,” Franken answered, adding: “So, we’re like a bridge over troubled ... " Silverman then interrupted with a laugh: “Oh, good lord.”

Though Simon wrote the title track for 1970's Bridge Over Troubled Water, it was Garfunkel's crystalline vocal turn that sent the song to the top of the Billboard chart. As such, some viewers were disappointed in Simon's performance. In the end, however, that's more a tribute to the original song's (and the original duo's) lasting power than Simon's solo update.

The 74-year-old Simon – who just released a well-received album, Stranger to Stranger – has hinted that his current tour could be followed by a retirement from show business.

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