At 68, he's past the usual retirement age, but Placido Domingo is still adding to a remarkable résumé that includes tenor, conductor and opera administrator. His latest assignment: baritone.

The inducement for this late-career vocal stretch was a chance to sing the title role in Giuseppe Verdi's Simon Boccanegra, one of the great parts for a singer with strong dramatic presence.

Domingo will make his debut as the Doge of Genoa on Saturday night in a new production at Berlin's Staatsoper unter den Linden. He'll also perform the role in New York, London, Zürich, Switzerland, Milan, Italy and Madrid, Spain.

"For many years, I had the dream of doing it," Domingo said Monday in an interview from Berlin. "It's one of those roles that all my life has been in my mind."

Private life

The music is magnificent, "and the character has almost the power of Shakespeare," he said. "We have both his private life in his reunion with his long-lost daughter, and his political role fighting for the unity of Italy, following the ideals of peace and love."

In a sense, the role marks coming full circle for Domingo. In 1959, still a teenager, he auditioned for Mexico's National Opera - as a baritone. The committee told him he was really a tenor. Since then, he has sung his way through 124 roles, opened the Metropolitan Opera season a record 21 times and become a celebrity far beyond the world of opera through his concerts and recordings as one of the Three Tenors.

Earlier in his career, Domingo sang the opera's tenor role, Gabriele Adorno, the young patrician who will eventually succeed Boccanegra and marry his daughter.

"But when I sang it, I was also thinking one day I will sing Simon if I can," he said.

Though he knew the music for the baritone part well, he said that when he began serious study three months ago, he found some surprises.

"I had to get used to using the middle part of the voice differently," Domingo said. "The notes around middle C, up to E-flat, the tenor voice just passes over them, but that's where a baritone has to make an impression ... .

"A singer doesn't sing only with one sound. Like a painter, you always have the palette for different colours."

Domingo said the Berlin rehearsals had gone "extremely well" and that he was feeling "very relaxed" about the opening. He's pleased to have Daniel Barenboim conducting and to have such stars as soprano Anja Harteros and bass Kwangchul Youn in the cast. The production, by Federico Tiezzi, is "mostly traditional," he said.

Dream

Antonio Pappano, music director of London's Royal Opera House, where Domingo will appear in the opera next summer, acknowledged in an interview earlier this year that the role "is a jump for him, there's no question".

"But it's a dream he's always had and, at this point of his career, you give him the benefit of the doubt," he told Hugo Shirley of the website MusicalCriticism.com

There's at least one more baritone role Domingo finds tempting, that of Athanael, the lovesick monk in Massenet's Thais.

And he's keeping busy with tenor roles now booking engagements through the 2013-14 season when he'll turn 73.

"When I decided to sing Boccanegra, the initial idea was to say goodbye with it," Domingo said. "But it didn't work out that way."

Placido Domingo