During the 1920s his compositions were championed by Arturo Toscanini; and Wilhelm Furtwängler, who permitted Kletzki to conduct the Berlin Philharmonic in 1925.

Because he was Jewish, he left Nazi Germany in 1933 and moved to Milan, Italy, where he taught composition.

During the Holocaust a number of Kletzki's family were murdered by the Nazis including his parents and his sister.

[1] He died on 5 March 1973 at 72 years of age after collapsing during a rehearsal at the Liverpool Philharmonic Orchestra.

From 1942 onwards Kletzki wrote no more compositions; he argued that Nazism had destroyed his spirit and his will to compose.