Boelzner, who underwent heart bypass surgery in recent years, died Wednesday at his New York home, the New York Times reported.
Boelzner joined City Ballet as a rehearsal pianist in 1959 and began to accompany performances soon after, the Times said. Boelzner eventually went on to conduct and was named music director in 1990. He retired in 1999 and assumed the title music adviser, which he still held at the time of his death.
Boelzner had a close working relationship with City Ballet founder and choreographer George Balanchine and was one of his favorite class accompanists, the Times said.
Boelzner is survived by a brother, Gary, of Irvine, Calif.