Fred Astaire and Ginger Rogers elevated each other, Katharine Hepburn is said to have observed: “He gave her class, and she gave him sex appeal.”

When Broadway stars perform with the San Francisco Symphony, the result can be a similar win-win. Divas with a giant orchestra behind them instead of strobe lights and swirling set pieces can draw focus to their musical craft, implying that their interpretations of Rodgers and Hammerstein are as much high art as pianist Yuja Wang’s take on Rachmaninoff. 

In turn, the singers, with their warmth and magnetism, make performing with the black-clad, usually stoic Symphony players look magical and exciting.

That’s why Sutton Foster and Kelli O’Hara’s appearance at Davies Symphony Hall was such a disappointing missed opportunity.

It’s not that the two Tony Award winners sounded bad on Saturday, July 18. Foster, with her glittery, reedy belt, is the perfect complement to O’Hara’s unvarnished airy soprano. Occasionally, as on the jazzy number “Great Adventure” from the musical “Kimberly Akimbo,” their voices somehow both sharpen and soften each other, like an oboe-flute duet.

The problem, rather, was the format.

Confoundingly, the concert drew on a 1962 TV special featuring Carol Burnett and Julie Andrews at Carnegie Hall  — as if Foster (TV Land’s “Younger” and “The Music Man,” “Anything Goes” and “Thoroughly Modern Millie” on Broadway) and O’Hara (HBO’s “The Gilded Age” and “Fallen Angels,” “The King and I” and “The Bridges of Madison County” on Broadway) weren’t A-list draws in their own right. The pair kept invoking their entertainment forebears, at one point even staging a dialogue with recordings of Burnett’s and Andrews’ voices, as if they thought there was some pent-up demand for a niche tribute the rest of us forgot about.

The evening’s patter — “As long as we’re havin’ fun!” — was painful. Song choices, with notable exceptions, failed to show the divas’ voices at their best. Multiple numbers, such as“Big D” from “The Most Happy Fella” and “They Don’t Let You in the Opera,” required Southern accents, and sometimes the only vocal quality audible above the orchestra’s volume was twang. 

Medley upon medley gave us too few chances to go deep with a musical idea or emotional arc, with an overall effect that was like swiping through TikTok videos. In one ‘90s medley, while it was hilarious to hear O’Hara suddenly bust out in Nirvana, the arrangement dragged on so long that the musicians seemed to be silently screaming, “Why?”

Not every concert by a Broadway star has to be the same. Delectable as it was to hear Foster’s sultry and sly opening glissando on “Anything Goes,” that doesn’t mean she and O’Hara must stick to their repertoire of best-known hits from their best-known shows. 

Yet there’s an impossibly vast canon of musical theater transcendence out there. Why sing novelty numbers your music directors wrote for you when we could get more renditions like O’Hara’s take on “If I Loved You” from “Carousel”? In that solo, her soprano was tremulous, and she brought the same focus and force whether her voice was a tiny pinhole of light or a blazing celestial orb. Conductor Michael Rafter brought out each piece of a chord — piano, harp, strings — like petals opening on a blossom.

That’s what most of us came to see. Except for Foster and O’Hara completists, this particular set list, which has been touring since a Carnegie Hall appearance in 2023, can stay in the ephemera box.