Wednesday night in New London’s Garde Arts Center, I witnessed the finest Yes concert I’ve ever experienced. And I’ve been to a few — by which I mean “a lot.”

The caveat? It wasn’t Yes.

Rather, 79-year-old Jon Anderson, the singer/songwriter who co-founded Yes before leaving the group some years ago, was in town as part of the “Yes Epics, Classics & More” tour. He appeared with the Band Geeks, who are NOT a tribute act but five New York City-based pals with solid professional pedigrees in various capacities.

Last year, Anderson, who has one of the most cherished voices and catalogs in rock, discovered the Geeks on YouTube. For fun and in their spare time, they’d posted a video of themselves playing “Heart of the Sunrise,” a glorious and anthemic piece from the Yes canon — the difficulty of which is similar to performing a spinal shrapnel extraction on a battlefield.

Anderson, yearning to hit the road at least one more time, reached out to the Band Geeks to see if they were interested in a collaboration. Excited in that “We just won the ‘Who Wants to Join a Rock Band with Their Hero’ sweepstakes” fashion, the Geeks, ah, joined a band with their hero.

Judging from the reaction in the Garde last night, you could say the partnership is working out really, really well. There were so many sustained up/down, up/down standing ovations from a mostly age-appropriate crowd — men and women who clearly grew up listening to Yes’ visionary progressive rock — that heart doctors and orthopedists should start prescribing Jon Anderson/Band Geeks concerts as cardio and joint rehab therapies.

Most importantly, Anderson can STILL hit those cathedral-ceiling notes in a ceaseless array of sublime melodies. Also crucial: The Band Geeks — bassist Richie Castellano, drummer Andy Ascolese, guitarist Andy Graziano and keyboardists Christopher Clark and Robert Kipp — are astonishingly good players. And singers! With those harmonies, they could probably get work at Early Music festivals as one of those Tallis Scholars-style a capella groups.

Or, as the soft-spoken Anderson said at one point in the 13-song, 110 minute show, “I was originally impressed with (the Geeks) because,” he grinned self-effacingly, “this music is really hard, and they can play it.”

Worth noting: they DO look sorta Geeky — IT Department chic, I’d say. But it works to their advantage because — particularly in a room as intimate as the Garde, with the facility’s sonically wonderful new sound system — you watched these Everymen pull off intricate masterworks with happy dexterity.

There’s no indication they’re intimidated by Anderson, who’s in great shape but still looked like a favorite eccentric uncle who dropped by to see “the boys” on a Hallmark holiday special. And he clearly enjoys being onstage with guys he regards as equals.

In addition to his flawless singing, Anderson took the stage wearing a light sport coat, dark pipe-cleaner slacks, and with his neck wrapped in a scarf he probably had to steal back from Prince. As he sang, Anderson still had that familiar and quasi-mystical performance choreography. He swayed, smiling beatifically, and slowly moved his arms over his head as though sending secret hand signals to woodland deities only he could see.

The performances were augmented by a triptych of vertical video screens that showed kaleidoscopic sequences that might have alternately been a nighttime campfire if your eyeglass lenses were made of dragonfly wings; slow-mo images of God’s dandruff floating through deep space; undersea plant life; and abandoned studio canvases by Roger Dean, the artist who created several iconic Yes album covers. It was all very … Andersony, and we wouldn’t have expected anything less to go with the music.

The first set was a streamroller of greatness with “Yours is No Disgrace,” “Perpetual Change,” “Close to the Edge,” “And You and I,” “I’ve Seen All Good People,” “Owner of a Lonely Heart” and “Heart of the Sunrise.” In the crowd, there was mounting excitement and awareness that something truly special was happening.

After a 20-minute break, we were reminded that Anderson and the Band Geeks have written, recorded and recently released an album called “True.” They featured three new songs, “Shine On,” “Thank God” and “True Messenger,” and each proved very Yes-worthy.

Those were interspersed with “Awaken,” an oft-overlooked masterpiece from Yes’ “Going for the One” recording, and the immortal “Starship Trooper,” with its gradually building “Würm” coda and a dynamic, rising full-band intensity behind Graziano’s forest fire soloing that staggered the crowd.

Finally, and perhaps inevitably, the evening came to a close with “Roundabout.” As maybe the classic Yes lineup’s most familiar song, it was a “wink-wink” reminder that, oh, yeah, even after Anderson and the Geeks had given us a transcendent processional of historic songs, it was probably time they played “the hit.”