After studying voice with Haldis Ingebjart in Stockholm and, later, Hartha Dehmlow in Berlin, Ralf made his debut in Stettin as Cavaradossi in a 1930 production of Tosca. He sang at Chemnitz in 1932 and 1933, then in Frankfurt from 1933 to 1935. In 1935, he began an eight-year association with Dresden, where he appeared as Apollo in the premiere of Strauss' Daphne in 1938. A recording made at the time testifies to Ralf's extraordinary facility in the very high tessitura of the role. Ralf's debut in London also took place in 1935 and he remained with Covent Garden until the outbreak of WWII made his return impossible. He revisited London once more in 1948, as Radames.
London critics appreciated Ralf at his first appearance on May 8, 1935 -- but the opera house administration liked him even more. He had come from Germany to substitute for an ailing singer in Lohengrin. Unable to book a flight, he traveled by ship and train, arriving just three and a half hours before performance time. His supple, yet powerful voice appealed greatly to the public and he became an instant favorite. Surprisingly, Ralf's Walter in Meistersinger the next season was felt to be lacking, but Ernest Newman wrote that his Parsifal was the finest he had ever heard. In November 1936, Ralf was a part of the Dresden Staatsoper ensemble visiting London and offered his Bacchus in a single performance of Ariadne auf Naxos, conducted by the composer himself. Ralf's reliability caused several critics to consider him an "absolutely safe" singer, not subject to the anomalies afflicting certain other artists.
During the period of hostilities, Ralf sang in Central Europe. On November 26, 1945, he made his debut at the Metropolitan Opera performing Lohengrin under the baton of Fritz Busch, himself new to the company. The critics were pleased with his smooth delivery of the hero's long narratives and a Tannhäuser three months later was regarded as positive. During the interim, Ralf's Walter elicited the opinion that no other tenor within memory had sung the role with so much freshness and ease. Under George Szell's firm direction, Ralf's Otello was fluent in the more lyric stretches, but short on the volcanic intensity needed for the dramatic outbursts. The eloquence Ralf brought to his Parsifal was as welcome at the Metropolitan in March 1947 as it had been in London. Ralf was a conscientious musician, seeking to follow the composer's intentions. When, however, he sang the final B flat at the conclusion of "Celeste Aida" softly as Verdi notated, his reward was only a smattering of applause. Several of his finest roles have been preserved on disc in both live and studio recordings. Among Ralf's recordings, the pre-WWII Meistersinger Act III is indispensable, showing his soaring tenor at its best. Ralf was only 53 at the time of his death.