art." Marcel Proust, greatly influenced by Wagner, refers to Tristan und Isolde and its "inexhaustible repetitions" throughout his novel In Search of Lost Time. He describes the prelude theme as "linked to the future, to the reality of the human soul, of which it was one of the most special and distinctive ornaments." Recordings Tristan und Isolde has a long recorded history and most of the major Wagner conductors since the end of the First World War have had their interpretations captured on disc. The limitations of recording technology meant that until the 1930s it was difficult to record the entire opera, however recordings of excerpts or single acts exist going back to 1901, when excerpts of Tristan were captured on the Mapleson Cylinders recorded during performances at the Metropolitan Opera. In the years before World War II, Kirsten Flagstad and Lauritz Melchior were considered to be the prime interpreters of the lead roles, and mono recordings exist of this pair in a number of live performances led by conductors such as Thomas Beecham, Fritz Reiner, Artur Bodanzky and Erich Leinsdorf. Flagstad recorded the part commercially only near the end of her career in 1952, under Wilhelm Furtwängler for EMI, producing a set which is considered a classic recording. Following the war, another classic recording is the 1952 performance at the Bayreuth Festival with Martha Mödl and Ramón Vinay under Herbert von Karajan, which is noted for its strong, vivid characterizations and is now available as a live recording. In the 1960s, the soprano Birgit Nilsson was considered the major Isolde interpreter, and she was often partnered with the Tristan of Wolfgang Windgassen. Their performance at Bayreuth in 1966 under the baton of Karl Böhm was captured by Deutsche Grammophon – a performance often hailed as one of the best Tristan recordings. Karajan did not record the opera officially until 1971–72. Karajan's selection of a lighter soprano voice (Helga Dernesch) as Isolde, paired with an extremely intense Jon Vickers and the unusual balance between orchestra and singers favoured by Karajan was controversial. In the 1980s recordings by conductors such as Carlos Kleiber, Reginald Goodall, and Leonard Bernstein were mostly considered to be important for the interpretation of the conductor, rather than that of the lead performers. The set by Kleiber is notable as Isolde was sung by the famous Mozartian soprano Margaret Price, who never sang the role of Isolde