Stephen Simon, a conductor who became a leading specialist in the compositions of George Frideric Handel and founded musical ensembles in Washington and New York, died Jan. 20 at a hospital in New York City after a stroke. He was 75.A family assistant, Lee Ryder, confirmed the death.Mr. Simon built a reputation as a Handel expert in the 1960s when he conducted some of the first recordings of many of the 18th-century composer's operas and oratorios.He was music director of the Handel Festival in New York from 1971 to 1974, and his recording of Handel's oratorio Solomon with the Vienna Volksoper Orchestra earned a Grammy Award nomination in 1969 for best choral recording."The idea that one would have all of the operas and oratorios recorded was something that we really couldn't have imagined at the time," said Donald Burrows, a Handel scholar in England.Mr. Simon settled in the Washington area to start the Handel Festival Orchestra in 1976. The orchestra, later known as the Washington Chamber Symphony, was a pivotal force in the revival of Handel's lesser-known works.Mr. Simon was an heir to the Annenberg fortune. He and his wife often used their own money to keep the orchestra afloat.His first marriage, to Ellen Friendly, ended in divorce. Survivors include Bonnie Ward Simon of Manhattan, his wife of 35 years; four sons from his first marriage; two from his second marriage; and four grandchildren.