Unusually for an opera singer, his family was not a musical one. When he was 11, a family friend encouraged him to join the church choir. He began to study sight-singing and piano, and at 13 he became the pupil of Frederic Anspach of the Brussels Conservatory. He was engaged by the Paris Opera in 1962, where he made his operatic debut in Berlioz's Les Troyens, as Priam and the Voice of Mercury. In 1964 he sang the role of Escamillo for the first time, appearing in this role countless times in the future and recording it no fewer than four times. In 1965, he joined the Geneva Opera, where he sang the role of Maitre Fal in the world premiere of Milhaud's La mère coupable. Lorin Maazel engaged him to sing in his recording of Ravel's L'heure Espagnol on Deutsche Grammophon and invited him to become a member of the Deutsche Oper. He made his La Scala and Covent Garden debuts in 1973; in 1974, was named a Berliner Kammersänger and won the German Music Critics' Prize; and in 1975, made his Metropolitan Opera debut.
During the 1970s and 1980s, he continued to add new roles to his repertoire and began his long-standing partnership with Herbert von Karajan and with the Salzburg Festival. As he and his voice matured, he dropped certain roles, such as Escamillo and Figaro, and added roles such as Philip II, the Flying Dutchman, and Simon Boccanegra. In 1983, he sang the title role in the world premiere of Messiaen's Saint-François d'Assise. He also continued to perform and record oratorio repertoire and became a noted interpreter of German lieder and French song, particularly the music of Henri Duparc. In the mid-'90s, he began again to explore new operatic repertoire, portraying Scarpia for the first time in 1995. He fared well in the inevitable comparisons to Gobbi. Both took a similar approach to roles -- studying the historical and literary sources for the character, but regarding them as supplementary to what the composer and librettist created.
He recorded widely for many labels. His aria recital CD on Forlane displays his versatility as an opera singer and his dramatic power. In the Wagner repertoire, his Amfortas in Karajan's recording on DG is a vivid depiction of that tormented king. In French opera, his Don Quichotte (EMI) under Plasson, brings out the humor, nobility, and pathos of the title role. He also was an admirable Leporello in the Losey film of #Don Giovanni., Rovi