[1] He performed and recorded with leading orchestras and opera companies throughout the United States and Europe, earning a reputation for exacting standards as well as an acerbic personality.

[3] In November 1937, Leinsdorf travelled to the United States to take up a position as assistant conductor at the Metropolitan Opera in New York City.

With the assistance of freshman Representative from Texas Lyndon B. Johnson,[4] he was able to stay in the United States, and became a naturalized American citizen in 1942.

[1][5] By the spring of 1943, the candidates being considered to take over for Artur Rodzinski as music director of The Cleveland Orchestra included Vladimir Golschmann of the St. Louis Symphony Orchestra, Albert Stoessel of the Juilliard School and New York Oratorio Society, George Szell of the Metropolitan Opera Company, and Leinsdorf, also of the Met.

[6] Given Leinsdorf's tender age (31) and limited experience conducting performances outside of opera, questions arose about his capacity for the job.

Among the most significant developments during Leinsdorf's first year in Cleveland was his intention to schedule the entire season in advance so the Orchestra could promote its concerts ahead of time and reach a wider audience;[7] his desire to have the Orchestra play a year-round schedule — though World War II complicated that possibility; and, finally, the successful negotiation of a weekly radio broadcast on Sunday evenings — allowing The Cleveland Orchestra to be heard throughout the United States, parts of Mexico, and by short wave across Europe, South America, and the South Pacific.

In October 1943, he received a letter informing him that his potential draft status had changed — though he remained doubtful he would be called to serve because of a host of health problems.

[11] Leinsdorf was still under contract, but he had lost much of his power as music director — compromising on a number of issues, from performance content to recording authority.

[2] On November 22, 1963, during a Boston Symphony concert, Leinsdorf had to announce the reports of President John F. Kennedy's assassination in Dallas, Texas, to a shocked audience.

Beginning 1957, Leinsdorf was conductor for a series of complete stereophonic opera recordings made in Rome, commencing with Puccini's Tosca with Zinka Milanov, Jussi Björling, and Leonard Warren for RCA Victor.

After leaving Boston in the 1970s, Leinsdorf returned to Decca/London to record several releases in their acclaimed Phase 4 Stereo project, notably Stravinsky's Rite of Spring and Petrouchka.

On August 17, 1967, Leinsdorf conducted the Boston Symphony Orchestra in a two-hour primetime special telecast in color on NBC, a reflection of the days when a commercial network would periodically broadcast a full-length classical concert.

[16]Ladies and gentlemen, we have a press report over the wires – we hope that it is unconfirmed, but we have to doubt it – that the President of the United States has been the victim of an assassination.