The end of Mahler’s Ninth Symphony contains some of the most spiritual and peaceful music ever written. So when a cellphone began ringing – and ringing, ringing, ringing without cease – during a performance by the New York Philharmonic on Tuesday evening, Alan Gilbert did something conductors virtually never do. He stopped the performance.

And then things really got bizarre.

Mr. Gilbert, the orchestra’s music director, said he turned to the area of Avery Fisher Hall where the sound was coming from, in one of the front rows, and asked the unknown miscreant to turn off the phone. (It was an individual who apparently failed to heed the recorded announcement from the actor Alec Baldwin to silence cellphones that is played before the Philharmonic’s performances.)

“Nothing happened,” Mr. Gilbert said in a telephone interview on Wednesday. “Nobody was owning up to it. It was surreal.” The phone kept ringing – the iPhone’s marimba ring-tone, according to the music blogger Paul Pelkonen, who wrote about the incident.

Mr. Gilbert said audience members pointed out two people sitting where the sound was coming from. “They were staring at me resolutely,” he said of the couple. Eventually, the man put his hand in his pocket and the ringing stopped. “It was so weird,” Mr. Gilbert said. “Did he think he could just bite his lip and soldier through?”

The conductor said he asked the man if he was sure the device was quieted. “Then he nodded his head,” Mr. Gilbert said. Guilty!

People in the hall had been shouting for the sound to stop. Mr. Pelkonen reported that they yelled: “Thousand-dollar fine!” “Kick him out!” “Get out!” Another blogger, who was present, Max Kinchen, wrote, “They wanted blood!”

Mr. Gilbert, in the interview, said: “It was so shocking what happened. You’re in this very far away spiritual place in the piece. It’s like being rudely awakened. All of us were stunned on the stage.”

The conductor then apologized to the audience for stopping, saying that usually it’s best just to ignore such a disruption, but this case was too much. The audience cheered and applauded. He then started the music again, picking a loud passage leading into the tranquil final minutes to begin.

Ringing cellphones are a common scourge of live performances, and indeed, most musicians soldier on. “Usually it’s not Mahler Nine you’re playing,” Mr. Gilbert said, “and usually it’s not the most emotionally wrought part of Mahler Nine, and usually people deal with it.”

He said he was convinced the sound was an alarm because of its continuous nature.

The policy at Avery Fisher Hall, run by Lincoln Center, where the Philharmonic is a tenant, is for ushers to approach the owners of ringing phones and ask them discreetly to turn off the devices, said Eric Latzky, the orchestra’s spokesman. “In this incident, unfortunately the policy was not followed,” he said.

Betsy Vorce, a spokeswoman for Lincoln Center, said officials were talking to the ushers involved. “This is one incident where the policy wasn’t followed,” she said. “We’re investigating it. We’ll take corrective action if necessary.”

The ushers do not answer directly to orchestra management, and Mr. Gilbert said no ushers were in sight at the time of the ringing. “I heard this morning that ushers in the hall claimed they didn’t hear it, which sounds ridiculous to me,” he said. “Everybody could hear it.”