Larry Desgaines sat on a piece of cardboard atop a damp rock near the mouth of a large sewer drain in Queens on a recent Friday evening. “It’s a privilege to be here,” he said, without irony.

It was just before sunset, and he was among a concert audience of about 50 people who were also perched on rocks, facing the waters of New York City Combined Sewer Outfall #BB 029, where the buried Sunswick Creek flows into the East River.

In the water, which, improbably, did not stink of sewage, two men in a canoe sat very still. The boat’s bow pointed toward land. As the sun dipped behind Roosevelt Island, another man sitting by the entrance of the tunnel banged on a metal pipe with a stick. The resulting sound was that of a ringing bell.

The canoe’s frontman, wearing a Tyrolean hat, yodeled: “Willkommen!” He drew out the final syllable, and his voice amplified and echoed in the tunnel. As the song ended, the canoe disappeared into the sewer, leaving only echoes behind.

This was the final evening of Drain Bamage, an unlikely concert organized by the musician and composer Stefan Zeniuk, along with experience designers N.D. Austin and Danielle Isadora Butler.

Mr. Austin and Ms. Butler are co-founders of the Tideland Institute, which encourages New Yorkers to treat their home as a maritime city, reimagining how various waterways might be used.

“The water in New York has just kind of become a backdrop to the city,” Ms. Butler said. “When actually, it is the why, and the how, of how the city was made — and how the city still functions.”

Mr. Austin has been involved in various watery, ephemeral experiences around the city over the years: a speakeasy in a shipping container, an extremely socially distanced desk floating on a raft in the East River, a bar inside a water tower.

Like his previous events, the sewer concert had a secretive, treasure-hunt aspect to it.

At 7:30 p.m., attendees gathered at the far end of a big box store, by a sign that read “Attention Shoppers.”

Instructions arrived via text message:

Follow the fenceline along the water. The sidewalk turns away from the river when it reaches a thick row of shrubbery hedge trees at the far end of the parking lot. Discreetly keep following the fence, *behind* the trees. There’s a small hole thru the fence. Be respectful of the fishermen.

One by one, people trickled down to the rocky shores of the East River and the banks of the underground creek turned sewer overflow. The concert was timed to correspond with low tide, allowing for watercraft to float into and out of the tunnel.

After the yodel echoes faded, there was a pause. Then came the silvery sound of a trumpet and the low moan of a tuba. Slowly, a wide barge emerged from the sewer, holding four horn players — Mr. Zeniuk was on saxophone — who performed as Mr. Austin and an associate kept the boat steady.

The horn piece, titled “Low Tide,” was composed especially for the night by Mr. Zeniuk. Foghorn-esque notes swirled and reverberated wildly, drowning out the noise from the adjacent parking lot.

For the musicians, much of the event’s allure was in the incredible, immersive, ricocheting acoustics produced by the sewer tunnel.

“It’s nature and magic, it’s chemistry,” said instrumentalist and singer Yuli Be’eri. “It’s alchemy. It’s all of it combined together.”

Ms. Be’eri followed the horn piece by emerging from the drain on a barge, playing a piano (from which the legs had been removed) while singing a song that was “partly made up, partly Hebrew poetry, partly random sounds.”

That evening, the skies were clear, but the concert was performed for four nights — including one during which New York City was in the grips of wildfire smoke drifting down from Canada.

“Wednesday, we weren’t even really sure if we were going to have a show, because that was the day that the entire sky was blood red,” Mr. Zeniuk said. Battling elements in order to sit next to a sewer made for a “communal sort of sort of situation,” he said. “It was really beautiful.”

The little cove by the water was quite peaceful. Birds tittered. Passing ferries created occasional waves, gently crashing against the rocks. Trees rustled in the breeze, and when people walked, there was the warm sound of dry leaves crunching and tiny twigs snapping.

Twilight set in, the dark crept around, and the show ended with another yodel. “Auf Wiedersehen,” sang the Tyrolean hatted man, Sylvester Schneider, from his perch in the canoe.

Ms. Butler thanked everyone for supporting New York’s “alternative underground culture.”

“It’s still alive!” she said.

As if on cue, a couple of bats, squealing and flapping, appeared near the drain opening and flew into the sky.

“Nowadays with social media, everything looks cooler than it is,” Ms. Be’eri said afterward. “Here, it was the opposite.”

She added: “Doing that was cooler than any picture of it you can ever see.”