In June of 1958, Leon Barzin left the National Orchestral Association and took up residence in Paris to spend more time with his wife and to conduct in Europe. At this time, Maestro John Barnett, an NOA alumnus, was invited to take over the post of Music Director and Conductor of the National Orchestral Association.

Maestro Barnett, a native of New York City, studied at the Manhattan School of Music, Columbia University and the National Orchestral Association. Under the Association’s Music Director, Leon Barzin, he commenced conducting studies at the age of 15, and at age 18 was awarded a scholarship from the New York Philharmonic Society for advanced studies in Europe at the Mozarteum Academy with Bruno Walter, Felix Weingartner and Nicolai Malko. Thereafter, he had private instruction from Professor Malko while touring Europe with him followed by study with Geores Enescu in Paris.

His professional conducting career commenced in New York when he was engaged as conductor of the New York Civic Orchestra. After successfully conducting a semester-long Beethoven Cycle at Columbia University as guest conductor of the New York City Symphony, he was elevated to the position of Principal Conductor of that orchestra. In its Carnegie Hall series, he acted as assistant to such internationally renowned conductors as Sir Thomas Beecham, Fritz Reiner and Otto Klemperer. On short notice, he took over two of Dr. Klemperer’s Carnegie Hall concerts.

On the west coast, he became Associate Music Director of the Los Angeles Philharmonic and Music Director of the world famous Hollywood Bowl. For over a decade, his name was well-known over the NBC Network of "Standard Hour" broadcasts with the Los Angeles Philharmonic. For a twenty-five year period, he was Music Director of the Los Angeles Guild Opera Company, working with the famous German Stage Director Dr. Carl Ebert in productions of The Magic Flute, Bartered Bride, Hansel and Gretel and Cenerentola – the young USC student Marilyn Horne making her debut in this role.

He was invited to return to New York to take over the post of Music Director and Conductor of the National Orchestral Association, continuing its program of training new generations of professional orchestral players, performing new contemporary works, and offering solo opportunities through its annual series of Carnegie Hall concerts. During his tenure, Barnett accompanied Itzhak Perlman in his Carnegie Hall debut.

Guest appearances in the United States have been with the Symphonies of San Francisco, Honolulu, Kansas City, Ft. Lauderdale, Phoenix and the Eastern Music Festival. He was the Founding Conductor of the Phoenix Symphony and the Japan-America Philharmonic in Tokyo. He has conducted abroad in Italy, Venezuela, New Zealand, Japan and throughout Asia, and has recorded for Capitol, Vanguard and CRI Records.

While Music Director of the Puerto Rico Symphony (1979-85), he also appeared as guest conductor of the Pro-Arte Concerts and the Casals Festival. He conducted the Opera de Puerto Rico productions of Madama Butterfly with Renata Scotto; Carmen with Placido Domingo; and Fille du Regimant with Alfredo Krauss. During the Symphony Seasons, he accompanied such soloists as Claudio Arrau, Paul Badura-Skoda, Rudolf Firkusny, Ruggiero Ricci, Yehudi Menuhin, Herman Baumen, James Galway, Schlomo Mintz, Itzhak Perlman and Ravi Shankar. Opera in Concert Programs included vocalists Kiri Te Kanawa, Birgit Nilssen, and, jointly, Renata Scotto with Placido Domingo.

Barnett has taught conducting and conducted the orchestras and opera performances at Stanford University, Claremont College’s Summer Session, the College-Conservatory of the University of Cincinnati and at the University of Southern California where he conducted the Symphony Conducting Program, and retired as "Head" of the Conducting Department.