Otto Nossan Klemperer was a German conductor and composer, originally based in Germany, and then the United States, Hungary and finally, Great Britain. He began his career as an opera conductor, but he was later better known as a conductor of symphonic music.
A protégé of the composer and conductor Gustav Mahler, from 1907 Klemperer was appointed to a succession of increasingly senior conductorships in opera houses in and around Germany. Between 1929 and 1931 he was director of the Kroll Opera in Berlin, where he presented new works and avant-garde productions of classics. He was from a Jewish family, and the rise of the Nazis caused him to leave Germany in 1933. Shortly afterwards he was appointed chief conductor of the Los Angeles Philharmonic, and guest-conducted other American orchestras, including the San Francisco Symphony, the New York Philharmonic and later the Pittsburgh Symphony, which he reorganised as a permanent ensemble.
In the late 1930s Klemperer became ill with a brain tumour. An operation to remove it was successful, but left him lame and partly paralysed on his right side.