It was one of those magical concert moments. Paul Simon was nearing the end of a sparkling concert at DAR Constitution Hall, having just brought the adoring, capacity crowd to its feet and inspiring every variety of awkward dance move with his 1986 hit “Diamonds on the Soles of Her Shoes.” Next came “Gumboots,” a zippy romp, also from the landmark “Graceland” album. As Paul stood stage center, smiling and singing with an added bit of elan, hearty cheers erupted and cellphones were unshackled to capture the moment.

Except it wasn’t Paul Simon doing the singing. It was . . . some dude. (We later found out his name is Paul Fournier, a local 42-year-old patent lawyer. For more on that, see The Reliable Source.) Simon missed his vocal cue on the song (he’s 69, give him a break) and then simply invited Fournier onstage to sing. The Other Paul had all the rock-star charisma of the original, which is to say none at all — short brown hair, a tucked-in button-up shirt, dark slacks, goofy grin. Yet he proved to be a complete natural. His rendition wasn’t simply passable, it was near perfect.

That the most memorable moment of the concert came with the star attraction happily observing was fitting. Simon’s status as an American songwriting superman is set in stone. He’s beyond simply receiving honors; new ones are basically invented to praise him. In 2007 he was awarded the Library of Congress’s Gershwin Prize for Popular Song, and part of the reason Simon was such a deserving inaugural recipient was on display Wednesday night. He exists to serve his songs and never the other way around. So if that means letting a patent lawyer sing the final song of a set or stepping aside to make room for an extended washboard solo, so be it. Simon is the creator and the vessel but doesn’t need to be the focus. He seemed to get as much joy simply sharing the stage with an eight-piece backing band of astounding musicians — each of whom excelled at multiple instruments — as singing his generation-defining songs.

Not that he didn’t share plenty of those from his nearly 50-year career. The first encore was a solo version of Simon & Garfunkel’s classic “The Sound of Silence.” (There wasn’t much stage banter from Simon, but he did say he remembered “playing here with Artie in the ’60s.”) “The Only Living Boy in New York,” “Still Crazy After All These Years” and “50 Ways to Leave Your Lover” were also clear fan favorites.

But songs from Simon’s new album, “So Beautiful or So What,” proved to be much more than excuses for a quick beer run. That album will make his trophy room even more packed come next year’s Grammys, and it’s easy to hear why. A song such as “Rewrite” showcased an almost-scientific mastery of songwriting, appealing to the brain, heart and hips all at once. He flicked his guitar as his band offered a gently rollicking rhythm, a sound that has become an unlikely and successful template for many current rock bands.

Simon sang in his usual low-key conversational cadence, offering lyrics that went from playful exercises in wordplay (“I been workin’ at the carwash / I consider it my day job / ’Cause it’s really not a pay job”) to simple and poignant. His still-sweet voice makes a chorus of “Help me, help me / Thank you / For listening to my prayer” sound especially comforting.

Simon also paid tribute to some of his songwriting heroes by covering tunes by Jimmy Cliff (a bouncy “Vietnam”), the Beatles (an elegant “Here Comes the Sun”) and trading guitar licks with bandleader Mark Stewart on the rock chestnut “Mystery Train.” On the surface, it seemed bizarre that someone with such an overflowing catalogue would take up precious set-list space with other people’s songs. But Simon’s not one to hog the spotlight. He wasn’t even the most scene-stealing Paul on this night.

Simon performs at the 9:30 Club on Friday night. The show is sold-out.