The fine bass singer, Karl Ridderbusch, first wanted to become a engineer. He was discovered at a singing competition by Rudolf Schock, who partly financed his musical education. From 1955, he studied at the Duisburg Conservatory, then from 1957 to 1961 at the Folkwangschule, Essen, with Clemens Kaiser-Brehme.
Karl Ridderbusch had his debut at Münster in 1961 (Philipp II., Commendatore, Mathis der Maler). From 1963 to 1965, he was a member of the Essen ensemble. During this three-year engagement he began to add the great Wagner, Strauss and Verdi roles to his repertoire. In 1965 he joined the prestigious Deutsche Opera am Rhein Düsseldorf-Duisburg (Sparafucile, Boris Godunow, Hunding). In 1967, he debuted at Bayreuth, which was the beginning of an international career. Until 1975, when he departed in anger from Bayreuth, he had sung Heinrich der Vogeler, Fasolt, Fafner, Hagen, Pogner, Hans Sachs, Hunding, Daland, Titurel, Koenig Marke. Other roles included Ochs auf Lerchenau, Monteverdi's Seneca, Donizetti's Henry VIII., Verdi's and Nicolai's Falstaff, Flotow's Plumkett, Cornelius's Barbier von Bagdad, Cardinal Madruscht in Palestrina, and numerous oratorio parts (Bach, Bruckner). He was a regular guest at the great opera houses of the world: La Scala (debut 1966), Metropolitan Opera (1967), Vienna State Opera (1968, Kammersänger 1978), Royal Opera House Covent Garden (1971), Paris (1967), Munich, Berlin, Hamburg, Salzburg Osterfestspiele (1968).
Karl Ridderbusch possessed a voice of rich colour, which, allied with his rock solid technique spanning a full 2 octaves, made him a formidable singer. In the opera house, his voice easily sliced through the thickest orchestra, with a diamond like brilliance to the tone, yet he always maintained an almost bel-canto tone, even at extremes of volume. This made his success in parts like Hans Sachs, The Flying Dutchman and Boris almost a foregone conclusion when he finally added them to his repertoire. He was a powerfully built man, and his impact on the stage in the great Wagner roles was almost as impressive as his voice. His other roles included Ochs in Der Rosenkavalier, Hunding in Die Walküre, and Hagen in Die Götterdämmerung.
Karl Ridderbusch died of severe heart condition and liver disorder at the age of 65 in June 1997, after his wife had taken him back to his home from an Austrian hospital the day before.