STOCKHOLM (AP) -- Spanish tenor Placido Domingo on Friday won the first $1 million Birgit Nilsson Prize for his "unrivaled" contributions to the world of opera, the award foundation said.

The late Swedish soprano picked Domingo as the winner of the inaugural award — billed as the biggest prize in classical music — before her death in 2005. Prize officials said the name had been kept secret for nearly a decade.

Nilsson, considered one of the greatest Wagnerian sopranos, sang with Domingo several times, the foundation said.

"She wanted to honor one of the greatest opera singers of all time, whose contributions to the world of opera and concert are unrivaled," Rutbert Reisch, president of the Birgit Nilsson foundation, said in a statement announcing the winner.

Domingo has performed in 130 roles and is celebrating his 40th season at New York's Metropolitan Opera. The 68-year-old singer won worldwide acclaim outside the opera scene as a member of The Three Tenors, with Jose Carreras and the late Luciano Pavarotti.

Nilsson's first performance with Domingo was at the Met in 1969 with a matinee production of "Tosca."

"Placido acquitted himself splendidly. He was an incredibly good Cavaradossi, his acting was superb — he was the part, he loved the part and on top there was gorgeous singing," Nilsson said afterward, according to the foundation.

Meeting journalists at Stockholm's waterfront Grand Hotel later Friday, Reisch said Nilsson had told him of the first award choice in the late 1990's. A few years later she sent him a sealed letter — to be opened three years after her death — but to his surprise the name was not included in the letter.

"In fact it was a personal letter and I guess she didn't find it necessary to repeat the name," he said, noting however that the soprano earlier "had clearly made up her mind on Placido Domingo."

Reisch described Nilsson and Domingo as similar in both style and personality. "That means impeccable musicianship, glorious voice and thorough professionalism. ... It's really a meeting of the minds."

Reisch said that Domingo, reached with the news late Thursday, had been "very touched, very moved, because the recognition by a legend in the same field that he is in, of course carries special weight."

Nilsson performed at the world's top opera houses during a career of almost 40 years. She died on Dec. 25, 2005, at age 87.

Toward the end of her career she decided to establish a foundation for a prize to be awarded every second or third year for outstanding achievements in opera and concert.

Subsequent winners will be decided by the foundation's council, which will take recommendations by a jury of prominent figures in classical music.

Reisch said the two once discussed various artists for the award, but that Domingo was the only name that had been firmly decided on from the start.

"She and I had a number of discussions and we came up with a half a dozen names that might potentially be candidates in the future, but that will be decided by the jury then and not by myself," he said.

A prize ceremony is planned for later this year in Stockholm, most likely to be held at the Royal Swedish Opera.