When you go to a concert of classical music in New York, the usher is likely to tell you, “Enjoy the show.” Well, two nights ago, Carnegie Hall had a genuine show — “Show Boat,” no less. The performance was a gala benefit for the hall itself.

Kern and Hammerstein wrote this musical in 1927, which was a good year for the Yankees, too. Both the show and the team have endured.

Carnegie Hall looked spiffy for “Show Boat,” with mood lighting and a little patriotic bunting. It was jarring to see the chorus segregated by race, on two sets of risers. But that’s “Show Boat.”

The lyrics, incidentally, were Bowdlerized, as usually happens in modern performances, and this is merciful.

This was not exactly a concert performance, and not exactly a staged performance — it was a mixture. And it was mostly staged, I would say. Robert Longbottom and Francesca Zambello handled their directorial responsibilities superbly. You can do a lot with a little if you have the imagination and wit. You don’t need crates of scenery and props.

Gregg Barnes served as “costume consultant” and, whatever that means, the show was gaily and enjoyably costumed.

Onstage was the Orchestra of St. Luke’s, conducted by Paul Gemignani. The orchestra played competently, and did not give the impression of slumming. Mr. Gemignani was an astute manager of affairs. He kept tempos on the brisk side, which was wise.

The cast was a mixture of classical singers and Broadway singers. And the blend worked. Frankly, it was sometimes hard to tell the difference. The cast was stocked with personality, heart, and fun.

All the singers were miked, which took some getting used to. It was especially unsettling to hear the classical singers miked. But you could forget about that by about the middle of Act 1.

The baritone Nathan Gunn certainly looks like a Ravenal, and he sang like one, too: dreamily. Sometimes this singing was crooning, but that was acceptable. Another classical singer, the soprano Celena Shafer, was Magnolia. She sang with both prettiness and strength, which is an achievement. And her acting was true.

Also able to sing and act is Carolee Carmello, a Broadway performer. She was Julie, and showed that character’s disintegration memorably. Ms. Carmello’s rendering of “Bill” brought the house down — and the house was right. This was an awesome turn.

Cap’n Andy? He was Jonathan Hadary, a jaunty, Southern Jiminy Cricket. Andy’s wife was Becky Ann Baker, a perfect, compact shrew.

Frank and Ellie were played by Gavin Lee and Megan Sikora. He is a long-legged wonder, a natural dancer, hard not to watch — a Dick Van Dyke of our day. She was full of spunk and sass, an Ado Annie — an Ellie, I should say.

The bass Alvy Powell, as Joe, sang “Ol’ Man River” with dignity and drama. He was not fully secure on high notes, but got by. And by the way, I remember another performance of “Ol’ Man River” in Carnegie Hall: Thomas Quasthoff sang it as an encore, after singing Bach’s holiest cantatas. Astonishing.

Alteouise deVaughn, a mezzo-soprano, was Queenie. She looked absolutely beautiful — warm and smashing. Her singing was less smashing, but adequate. Her presence was the main thing.

And the little girl in the part of Kim sang brassily. (Think “Annie” style.) Why do they teach little Broadway girls to sing this way? Or do they do it naturally?

The best singer in the house was one of the best singers of all time: Marilyn Horne. She will soon turn 75, and she did not sing. She spoke the lines of the Lady on the Levee. She put on a cornpone accent, did this native of Bradford, Pa. She wasn’t foolin’ anybody.

Regardless, it was wonderful to see her. Thrilling, even. But, oh, to have heard her sing one note — just one.

There was nothing wrong with this “Show Boat.” Not one thing. And pretty much everything right. Tuesday night was a very, very happy time in Carnegie Hall. Why don’t they put on a show again?