The final strains of “Arirang”, the heart-rending Korean folk song about separation, had not even ended when the thumping applause started filling the East Pyongyang Grand Theatre on Tuesday night.

Middle-aged men with purple-tinted glasses and women in traditional dress, visiting South Korean sponsors and Manhattan matrons in fur, they all leapt to their feet to celebrate the New York Philharmonic’s emotionally charged debut performance in Pyongyang.

It felt like history.

Expectations were high for this trip, where the US’s most prestigious orchestra went to a country founded on hatred of America. Just as cultural exchanges helped transform the US’s relationship with China and the Soviet Union, some hoped this would be the beginning of warmer relations, and perhaps even détente, with North Korea. But few could have dared to hope the performance would have been so well received.

From the start, the concert was exceptional. On a stage flanked by North Korean and US flags, the orchestra played “Aegukga”, the North Korean national anthem, and the “Star Spangled Banner”. This would have been unthinkable 18 months ago.

The New York Phil moved on to Dvorak’s New World Symphony. The applause was the kind of applause the audience might usually give at a revolutionary opera about agricultural production. The mood changed when Lorin Maazel, music director, turned to introduce the next piece. “It is written by America’s most well-known composer and it’s called An American in Paris,” he explained. “Some day a composer might write a work entitled Americans in Pyongyang.”

The audience broke out into rapturous applause. The ice was broken. If this concert precipitates a thaw, it started here.

Unlike with the Dvorak symphony, the members of the audience seemed to respond to the Gershwin piece. Indeed, Dvorak and the like are de rigeur in North Korea, but Gershwin is something else. The audience as a whole suddenly seemed much more engaged.

Many North Koreans were quick to join the standing ovation. And then the fireworks began. For the encore, the orchestra played Leonard Bernstein’s Candide, after which Mr Maazel explained the orchestra’s special attachment to its former conductor.

“Imagine Maestro Bernstein coming back and conducting once more,” Mr Maazel almost whispered. “Maestro, do me a favour,” he said in Korean, backing off the stage to leave the orchestra to play Bizet’s Farandole without him.

The sight of the empty green dais was spine-tingling, especially given the historical connotations: Bernstein led the Phil to the Soviet Union in 1959.

The real magic came last.

“ ‘Arirang’, ‘Arirang’,” the North Koreans whispered to each other as the violins played the opening notes. The people in the second and third circles leant forward to watch over the ledge. The piccolo peeped the tune, the violins sang languidly.

As the piece closed, the applause was electric. And it was put on full display something rarely seen in North Korea: spontaneity.

The entire audience was on its feet, but this time it was not just the women in traditional dress who were smiling, it was the previously implacable bureaucrats too. They clapped, as the orchestra bowed.

Even as the musicians left the stage, the applause continued for several minutes. As Mr Maazel and the concert master returned to the empty stage, some North Koreans applauded over their heads.

“It seemed they were being so friendly with us through the music,” said one North Korean woman in a peach-coloured traditional dress, white handkerchief in her hand. “My favourite was ‘Arirang’. I felt very moved.”

Mr Maazel was also clearly moved. “It was a stunning, stunning reaction. We haven’t seen that kind of enthusiastic reaction in a long time, and we have had some very successful concerts,” he said after the concert. “When we saw that very enthusiastic reaction, we thought that maybe it was mission accomplished.”