Opera star Placido Domingo received a standing ovation for his 50th anniversary gala concert at La Scala on Sunday and returned the appreciation with a rare a cappella performance.

Standing alone on the stage holding three yellow roses, Domingo serenaded the audience with a favorite Spanish zarzuela, “Non Puede Ser.” By then, after more than half an hour of applause and a standing ovation rare for the storied Milan opera house, Domingo and his co-stars for the evening, the choir and orchestra had already performed two encores. He alone emerged for the third.

Domingo, 78, appeared overwhelmed by the reception, and at one point kissed the stage where he performed for the first time on Dec. 7, 1969, in the title role of Verdi’s “Ernani.” In all, he has sung 135 times on the La Scala stage, in 22 operas.

FILE - In this July 12, 2019, file photo, opera singer Placido Domingo speaks during a news conference about his upcoming show "Giovanna d'Arco" in Madrid, Spain. Two opera singers who have accused Domingo of sexual misconduct reacted angrily to his claims in recent interviews that he never behaved improperly and always acted gallantly and like a gentleman with women. Angela Turner Wilson and Patricia Wulf issued a statement Tuesday, Dec. 3, 2019, saying they found Domingo's comments and his "continued failure to take responsibility for wrongdoing" to be disappointing and deeply disturbing. (AP PhotoBernat Armangue, File)

FILE - In this July 12, 2019, file photo, opera singer Placido Domingo speaks during a news conference about his upcoming show "Giovanna d'Arco" in Madrid, Spain. Two opera singers who have accused Domingo of sexual misconduct reacted angrily to his claims in recent interviews that he never behaved improperly and always acted gallantly and like a gentleman with women. Angela Turner Wilson and Patricia Wulf issued a statement Tuesday, Dec. 3, 2019, saying they found Domingo's comments and his "continued failure to take responsibility for wrongdoing" to be disappointing and deeply disturbing. (AP PhotoBernat Armangue, File)

The La Scala anniversary fell during a year that has seen U.S. opera houses cancel Domingo’s scheduled appearances, following reports by The Associated Press that more than 20 women had accused the star of sexual harassment or inappropriate sexually charged behavior.

Domingo has denied the allegations, and after a period of silence, only recently has begun giving interviews to select publications ahead of European appearances. In the interviews he claimed he always behaved like a gentleman and said he never abused his power. He also has said he intends to continue performing at least through his planned engagements running through 2021.

While in the United States all of his published dates were canceled, the singer has received overwhelming support from Europe's opera houses — which have all maintained his dates — and fans alike.

Opera star Placido Domingo performs during a concert at the Elbphilharmonie in Hamburg, Germany, on Wednesday, No. 27, 2019. (Christian Charisiusdpa via AP)

Opera star Placido Domingo performs during a concert at the Elbphilharmonie in Hamburg, Germany, on Wednesday, No. 27, 2019. (Christian Charisiusdpa via AP)

Many at Sunday's performance focused on the quality of his voice, its unique timber, while weighing the art against the impossibility for outsiders to know what happened between Domingo and his accusers.

“I’m very much impressed. Placido Domingo’s voice is still unbelievable, if you see how old he is,’’ said Doris Papst, 80, who traveled with a group from Baden-Baden, Germany, for the gala concert. “What has happened with him with #MeToo in the United States is horrible. We all have to answer in our lives for our behavior. We should not be the judges.”

Giuseppina Uscidda has been following Domingo at La Scala for 40 years, and said the long applause was well-deserved.

Opera star Placido Domingo performs during a concert at the Elbphilharmonie in Hamburg on Wednesday, No. 27, 2019. (Christian Charisiusdpa via AP)

Opera star Placido Domingo performs during a concert at the Elbphilharmonie in Hamburg on Wednesday, No. 27, 2019. (Christian Charisiusdpa via AP)

“His voice is beautiful,’’ Uscidda said. “This evening makes clear how much the audience loves him.”

A couple of dozen fans waited outside until midnight to greet the star, and they weren’t disappointed. The Spaniard came downstairs and stood behind a reception desk, where he started signing autographs.

“I saw him for the first time in Hamburg in 1978 and since then I am a convinced Domingo admirer,’’ said one of those waiting, Dagmar Engdken, citing not only his artistic abilities but also his social engagement for people in need, including benefit concerts.

“I will come hear him as long as I can, and as long as he sings,” Engdken said.