[3] By 1930 Barnett had received awards for his trumpet and piano playing, winning two silver medals in the Junior Division at the New Jersey State Musical Contest at Newark.
[5] At the age of 15, he received a five-year scholarship for the period 1932-37 from the Philharmonic-Symphony Society of New York to learn orchestral conducting, advanced music theory, composition and piano.
[6] He had been studying the cornet since the age of ten with Moscow-and-Berlin-trained, New York Philharmonic cornetist/trumpeter Max Schlossberg (1873-1936), who was considered to be "the Founder of the American School of Trumpet Playing in the Twentieth Century".
[11] Barnett began his professional career in 1931, when he was accepted into the National Orchestral Association under conductor Léon Barzin,[12] with whom he studied conducting for five years.
In June 1936, accompanied by Barzin, Barnett sailed to Europe to study for a year in Paris, Romania, London and other European cities.
[15] Barnett studied at the Mozarteum Academy in Salzburg, Austria, with conductor Bruno Walter, Felix Weingartner and the Vienna Philharmonic.
[22] Barnett was awarded the position of Principal Conductor of The New York City Symphony Orchestra in 1939 after guest conducting a semester-long Beethoven Cycle at Columbia University.
[25][26][27] In January 1945 he conducted a War Bond Concert at the Civic Music Center in New York City,[28] which was broadcast by WQXR Radio.
[33] During his years in California, Barnett served as Associate Conductor of the Los Angeles Philharmonic, Music Director of the Hollywood Bowl and of the Pacific Coast Music Festival, Conductor of the Phoenix and San Diego Symphony Orchestras, and for over ten years he also conducted the NBC Network’s "Standard Hour" broadcasts of the Los Angeles Philharmonic.
[34][35] After serving for two seasons with the Los Angeles Philharmonic, 30-year-old Barnett was appointed conductor of the newly-formed Phoenix Symphony Orchestra.
[41] On February 20, 1956, Barnett was named the conductor of the Guild Opera Company of Los Angeles,[42] a position he was to hold for twenty-five years.
Later in 1956, Barnett and the 92-member Los Angeles Philharmonic began a 60-concert nine-week goodwill tour the free Far East under the sponsorship of the State Department and the American National Theater and Academy.
Uncommon during the time, it was the first major orchestra in the Western United States chosen for an international cultural exchange program with the Orient.
[45] The tour included stops in Manila, Bangkok, Singapore, Kuala Lumpur, Hong Kong, Taipei, Okinawa, Seoul, and 11 cities in Japan[46] (Tokyo, Yokohama, Shizuoka, Osaka, Hiroshima, Kokura, Fukuoka, Kyoto, Otsu, Sapporo[47] and Nagoya).
[48] The Orchestra premiered its first concert on April 30 in the sweltering mid-90-degree heat and high humidity of Manila, where a crowd of more than 3,000 people attended, 2,500 of them sitting in squeaky rattan-bamboo chairs provided at the Mapua Memorial Hall, usually used as a sports arena, with many more listening from outside the venue.
Because the violin was a popular "Western" instrument in Singapore, Barnett spent an entire morning at the Goh Soon Tioe School of Music working on Mozart’s 26th Symphony with 20 Chinese, Indian and Eurasian children string players ranging in age from six to twenty-four.
Chiang Kai-shek, who welcomed the Orchestra wholeheartedly, seeing the tour as a way to win over the Southeast Asian people’s hearts and minds in this tumultuous post-war era.
[56] Following the tour, the then 39-year-old Barnett was invited by the United States Information Service (USIC), the agency responsible for U.S. cultural programs abroad, to form and conduct the 96-piece bi-national Japan-America Philharmonic Orchestra in Tokyo.
The Orchestra’s tour was co-sponsored by the United States Information Service of the American Embassy in Tokyo, and the Japanese Cultural Organization.
Barnett said in a Los Angeles Times article dated September 22, 1957 that the goal of the Orchestra (and the American Embassy) was to put on higher-quality concerts for the average Japanese for the same low price the "leftists" were providing, and also to show camaraderie between Japanese and American musicians working together to overcome any lingering resentment still existing after the war.
He had played as a youth in the Association’s trumpet section and had benefited from its conductor-training program when he went abroad in 1936 to study conducting with some of the world's most famous conductors.
Paul Affelder described the National Orchestral Association in his original liner notes circa 1968 from the Composers Recordings Inc. (CRI) LP of "Music of Wallingford Riegger" (conducted by John Barnett in 1967).
[61] While Musical Director of the National Orchestral Association, Barnett championed new performers and composers, which resulted in many accolades for his work.
[34] In addition to his work with the Association, Mr. Barnett served as Music Director of the Philharmonic Symphony of Westchester (New York) and continued to direct the Guild Opera Company of Los Angeles.
While in Puerto Rico, he was quite active in opera, conducting stage productions featuring such great operatic artists as Renata Scotto, Placido Domingo, Alfredo Kraus, Kiri Te Kanawa, and Birgit Nilsson.
In keeping with the National Orchestral Association’s teaching philosophy which influenced him greatly, Barnett’s later years were dedicated towards nurturing promising musicians in higher education.