So what if there’s nothing significantly new on Simon & Garfunkel’s two-CD live retrospective? Recorded last year at Madison Square Garden and the New Jersey’s Continental Airlines Arena, the triumphant “Old Friends: Live on Stage” finds the divorced/ reunited duo making its first appearance side by side in 20 years. S&G deliver more than 20 of their classic songs, sparked back to life. The performance supports the premise that the duo ranks among the top creative partnerships of the ’60s. The bulk of the songs are Simon compositions rendered with whimsy and beauty, angst and spunk—all with S&G’s trademark vocal harmonies. Highlights include between-song banter about their arduous friendship and a “Bye Bye Love” cameo by mentors the Everly Brothers. The dividend: a remarkably apropos new studio song, “Citizen of the Planet,” penned in the early ’80s but left unfinished.—DO