Powerful of voice, though without the deep, cutting tone of some of his predecessors, bass Karl Ridderbusch nevertheless made a strong impression in the great Wagner bass roles. His plush instrument boasted thrusting top notes during the years of his considerable prime and possessed sufficient size to dominate a large orchestra. In addition, its fine focus made him a splendid singer of Bach, as was evidenced by his beautifully sung Christus in the composer's St. Matthew Passion. Originally trained in engineering, Ridderbusch turned to singing when he won an amateur competition and was noticed by German tenor and TV personality Rudolf Schock. Schock was sufficiently impressed to help underwrite a program of studies at Essen's Folkwangschule. Ridderbusch made his stage debut at Münster's Städtisches Theater in 1961 and shortly thereafter accepted a contract at Essen where he began to undertake the Wagner, Verdi, and Strauss roles that would form the core of his subsequent repertory. In 1965, he joined the Deutsche Oper am Rhein. In 1966, he made his American debut singing Sarastro with Lyric Opera of Chicago and in 1967, he first appeared at Bayreuth. Ridderbusch made his first Metropolitan Opera appearances in 1967 and sang in an impressive Ring cycle at Covent Garden in 1971. His Hagen, somewhat heartier than most, was nonetheless a dangerous personality and was vigorously sung. Meanwhile, he had begun a long-term relationship with the Wiener Staatsoper and was frequently heard in Munich as well. Soon, he came into conductor Herbert von Karajan's circle of preferred singers and became a regular at the Salzburg Easter Festivals and in the conductor's related recording projects. During the period in which he was Karajan's leading bass of preference, Ridderbusch recorded such roles as Pogner in Die Meistersinger, Marke in Tristan und Isolde, Heinrich in Lohengrin, Hagen in Die Götterdämmerung, and Rocco in Fidelio. Nor was he unaccustomed to recording with others. Daland and Falstaff in Nicolai's Die lustigen Weiber von Windsor were sturdy interpretations sung under the direction of other leading conductors. Given his facility in the top register, Ridderbusch moved to undertake Hans Sachs and quickly became one of the role's leading proponents. His Sachs in the Chicago Lyric Opera's 1977 production of Die Meistersinger was, if somewhat bluff, richly and warmly sung.