See his Minor Recollections (1964).
Klemperer studied music first at the Hoch Conservatory in Frankfurt, and later in Berlin under Hans Pfitzner. In 1905 he met Gustav Mahler while conducting the off-stage brass at a performance of Mahler's Symphony No. 2, 'Resurrection'. The two became friends, and Klemperer became conductor at the German Opera in Prague in 1907 on Mahler's recommendation. Mahler wrote a short testimonial, recommending Klemperer, on a small card which Klemperer kept for the rest of his life. Later, in 1910, Klemperer assisted Mahler in the premiere of his Symphony No. 8, Symphony of a Thousand.
Klemperer went on to hold a number of conducting posts, in Hamburg (1910-1912); in Barmen (1912-1913); the Strasbourg Opera (1914-1917); the Cologne Opera (1917-1924); and the State Opera in Wiesbaden (1924-1927). From 1927 to 1931, he was conductor at the Kroll Opera in Berlin. In this post he enhanced his reputation as a champion of new music, playing a number of new works, including Leoš Janáček's From the House of the Dead, Arnold Schönberg's Erwartung, Igor Stravinsky's Oedipus Rex, and Paul Hindemith's Cardillac.
In 1933, once the Nazi Party had reached power, Klemperer, who was Jewish, left Germany and moved to the United States. Klemperer had previously converted to Catholicism, but eventually returned to Judaism. In the U.S. he was appointed Music Director of the Los Angeles Philharmonic Orchestra. He took United States citizenship in 1937. In Los Angeles, he began to concentrate more on the standard works of the Germanic repertoire that would later bring him greatest acclaim, particularly the works of Beethoven, Brahms and Mahler, though he gave the Los Angeles premieres some of fellow Los Angeles resident Arnold Schoenberg's works with the Philharmonic. He also visited other countries, including England and Australia. While the orchestra responded well to his leadership, Klemperer had a difficult time adjusting to Southern California, a situation exacerbated by repeated manic-depressive episodes, reportedly as a result of severe cyclothymic bipolar disorder.
Then, after completing the 1939 Los Angeles Philharmonic summer season at the Hollywood Bowl, Klemperer was visiting Boston and was incorrectly diagnosed with a brain tumor, and the subsequent brain surgery left him partially paralyzed. He went into a depressive state and was placed in institution; when he escaped, The New York Times ran a cover story declaring him missing, and after being found in New Jersey, a picture of him behind bars was printed in the Herald Tribune. Though he would occasionally conduct the Philharmonic after that, he lost the post of Music Director. Furthermore, his erratic behavior during manic episodes made him an undesirable guest to US orchestras, and the late flowering of his career centered in other countries.
Following the end of World War II, Klemperer returned to Continental Europe to work at the Budapest Opera (1947-1950). Finding Communist rule in Hungary increasingly irksome, he became an itinerant conductor, guest conducting the Montreal Symphony Orchestra, WDR Orchestra Koln, Concertgebouw Orchestra, and the Philharmonia of London. His career was turned around in 1954 by the London-based producer Walter Legge, who recorded Klemperer in Beethoven, Brahms and much else with his hand-picked orchestra, the Philharmonia, for the EMI label. He became the first principal conductor of the Philharmonia in 1959. He settled in Switzerland. Klemperer also worked at the Royal Opera House Covent Garden, sometimes stage-directing as well as conducting, as in a 1963 production of Richard Wagner's Lohengrin.
Klemperer is less well known as a composer, but he wrote a number of pieces, including six symphonies, a Mass, nine string quartets and the opera Das Ziel. He seldom performed any of these himself and they have generally fallen into neglect since his death, although Klemperer's works have received the occasional commercial recording.
A severe fall during a visit to Montreal forced Klemperer subsequently to conduct seated in a chair. A severe burning accident further paralyzed him, which resulted from his smoking in bed and trying to douse the flames with a glass of whisky. Through Klemperer's problems with his health, the tireless and unwavering support and assistance of Klemperer's daughter Lotte was crucial to his success. His son, Werner Klemperer, was an actor and became known for his portrayal of Colonel Klink on the US television show Hogan's Heroes.
Klemperer had taken Israeli citizenship in 1970. He retired from conducting in 1971. Klemperer died in Zürich, Switzerland in 1973, aged 88, and was buried in Zurich's Israelitischer Friedhof-Oberer Friesenberg.
Similar, if less extreme, reductions in tempos can be noted in many other works for which Klemperer left multiple recordings, at least in recordings from when he was in his late 70s and his 80s. For example:
(a) the Symphony No. 38 ("Prague") of Mozart, another Klemperer specialty. In his concert recording from December 1950 (when he was 65 years old) with the RIAS Berlin Orchestra the timings are I. 9:45 (with repeat timing omitted; the performance actually does take the repeat); II. 7:45; and III. 5.24. In his studio March, 1962 recording of the same work with the Philharmonia (recorded when he was 77 years old), the timings are notably slower: I. 10:53 (no repeat was taken); II. 8.58; III. 6:01. Unlike the late Eroica, the 1962 Prague is not notably slow; rather, the 1950 recording is much faster than most recordings of the work, even by "historically informed" conductors.
(b) The Anton Bruckner Symphony no. 4 (Haas edition with emendations). A 1947 concert recording with Concertgebouw has timings of I. 14:03; II. 12:58; III. 10:11; and IV. 17.48. The studio recording with the Philharmonia from 1963 has timings of I. 16:09; II; 14:00; III. 11.48; IV. 19:01. Again, the 1963 is not a notably slow performance, but the 1947 was quick.
Regardless of tempo, Klemperer's performances often maintain great intensity. Eric Grunin, in a commentary on the "opinions" page of his Eroica Project, notes: "....The massiveness of the first movement of the Eroica is real, but is not its main claim on our attention. That honor goes to its astonishing story (structure), and what is to me most unique about Klemperer is that his understanding of the structure remains unchanged no matter what his tempo... "
A list of historical recordings of the Los Angeles Philharmonic with Klemperer conducting (including parts of the George Gershwin Memorial Concert at the Hollywood Bowl can be found here: Otto Klemperer conducting the Los Angeles Philharmonic
Klemperer's last recording was Mozart: Serenade in E-Flat, K.375, recorded Sept. 28, 1971. That recording session was the last time he ever led an orchestra.