Perhaps it's a stretch to suggest that if we were suddenly transported back to the 1970s, fistfights might have erupted after — or even during — Jeremy Denk's performance of Bach's Chromatic Fantasy and Fugue in D minor on — heaven forbid — a modern grand piano.

The aesthetic debate — harpsichord vs. piano — is not so heated these days. In the '70s, however, when the early music movement was shifting into high gear and when expert harpsichordists such as Anthony Newman and Gustav Leonhardt were causing a stir with their Bach recordings, this was an issue. Playing Bach's pristine harpsichord music on a big, vulgar, gas-guzzling, Cadillac-size concert grand was a "travesty," wrote one critic.

But, argued defenders of the piano, wouldn't Bach have preferred today's keyboards if he had had that option? And didn't he make transcriptions of his own works? Good arguments. A better one: Harpsichords are hard to hear in today's big concert halls. Even better: When you've got a pianist as brilliant as Denk waiting in the wings, and one who happens to be a Bach specialist, the case is closed, more or less.

Denk opened his concert with the St. Paul Chamber Orchestra on Friday night at Ordway Concert Hall playing the Fantasy and Fugue — and playing it from memory, amazingly. (Denk is an SPCO Artistic Partner.)

As his much-praised recording of the "Goldberg Variations" shows, Denk is able to deliver Bach's complicated lines with maximum clarity while addressing the music's emotional power. His tempos were flexible — much use of rubato — and his phrases were warmly shaped. The varied colors that the modern piano can produce, in distinction to the monochromatic harpsichord, were abundantly on display.

Surely Bach, had he been present, would have joined the audience in enthusiastic applause.

One wondered: Do the same arguments apply to Rudolf Barshai's arrangement for strings and winds of Shostakovich's String Quartet No. 3, which the orchestra played just before intermission? Perhaps not. In Barshai's hands, it's a different piece, less intimate, less subtle, not nearly so plaintive in character as the original — new wine in a new bottle. Nonetheless, the orchestra, led smartly by concertmaster Steven Copes, played vigorously with warm tone and tight ensemble.

Denk returned to the stage after intermission, joining the orchestra in Beethoven's Piano Concerto No. 4, the most inward and poetic of Beethoven's concertos.

Copes and Denk shared the conductor's role from their seats, and the result, despite a few ragged moments in the orchestra, was attentive at the very least. Denk played exquisitely, with a touch smooth and light, giving the phrases a serene, beautifully pellucid arch. He played the longer of the two first-movement cadenzas, observing all the notes while adding an aptly improvisatory quality.

Denk will return to the orchestra with a different program next weekend.

Michael Anthony is a Twin Cities classical music critic.