Sting led his Broadway cast of “The Last Ship” through a semi-private show last night at 54Below.

The Tony nominated score in concert was supposed to serve as a 10th anniversary tribute to raise money for Project ALS. One star of the original cast, Aaron Lazar, has been diagnosed with the condition.

Many of the original cast and orchestra showed up to two packed performances back to back at the beautiful space below Studio 54. The remarkable Fred Applegate, Rachel Tucker, Sally Ann Triplett, and Shawna Mahic were among those who flew in on their own dime from far flung places, ready to put on a show.

But a couple of the leading men were tied up with other projects. Who took their places at the last minute? Sting, of course. The international rock star wound up singing more than half the show he wrote more than a decade ago. It was an unexpected treat.

Sting explained to the crowd that the men were AWOL. Otherwise, he cracked wise, “I don’t need this much fucking attention!”

He opened the show with “All This Time,” and later crooned “Dead Man’s Boots,” “The Night the Pugilist Learned How to Dance,” “Jock the Welder,” and most notably, “What Say You, Meg?” — the brilliant number sung by Lazar in the show. On a video piped into the room, Lazar recounted how Sting came to him during previews and said, “I wrote a song for you.” They went with musical director Rob Mathes into a rehearsal room, where Lazar’s mind was blown. “What Say You Meg?” is now a classic. Hearing Sting himself sing it last night was a slice of nirvana.

Mathes was the music supervisor last night, and the show was directed uniquely by Tom Ridgely. It’s not easy to fit a whole Broadway show with a big cast into a small space and onto an even smaller stage, but Ridgely did it by placing a sizeable chorus of singers on the other side of the room, nestled among the audience. The result was a spine tingling sonic wonder.

What a night! Broadway veteran Fred Applegate led the finale of the title song with great poignancy. Fred came in from his semi-retirement in California with his wife and son, Ethan, who sang with the chorus. (Note: Fred is always available, he says, for the right role!)

And Sting? What can you say? He’s in the middle of his 3.0 Tour but took a pause to put on the night. His voice is one of the wonders of the world, it just gets better and better. His sense of humor and spontaneity never fail him, either, as the night had one or two “flubs,” but he rolled with the punches. Listening the score, “The Last Ship” seems ready for a revival at maybe Encores! The songs — even the ones that were cut — are a melodic miracle.

Here’s Aaron Lazar from the original show, followed by clips from last night: