Lloyd Geisler, 90, who played first trumpet with the National Symphony Orchestra for 37 years and was its associate conductor for concerts in the parks and at Wolf Trap and other performance centers, died Dec. 30 in Brackney, Pa., while visiting the home of his stepdaughter. He had heart ailments.

Mr. Geisler stepped up to became the unofficial assistant conductor in 1957, when conductor Howard Mitchell was late getting back from a guest tour in Europe. He rehearsed the orchestra during other times when Mitchell was away and conducted concert series that included pops concerts, young peoples concerts and the orchestra's Summer in the Parks series.

He was named associate conductor in 1961 and retired in 1973. He had lived since the 1970s in Myrtle Beach, S.C.

Mr. Geisler graduated first in his high school class in his native Pottstown, Pa., during the Depression. He later recounted how he had startled his friends and family by turning down a good job in a local bank and then winning a scholarship to the Curtis Institute in Philadelphia. Music was not necessarily regarded as a promising profession at the time, he said.

While in school, he played in dance orchestras, bands and theaters, and was recruited by Leopold Stokowski to play in his studio orchestra six nights a week. When he graduated, he followed classmate Howard Mitchell to the National Symphony, where the conductor, Hans Kindler, immediately offered him the principal trumpet chair.

Mr. Geisler took wartime leave to play with the U.S. Navy Band, and returned to the symphony in 1946.

He taught conducting and trumpet at Peabody Conservatory and Catholic University and at his Arlington home. He also was the musical contractor for events in the area, including the Washington Opera.

Mr. Geisler was the founding president of the International Trumpet Guild. He sold all his trumpets when he moved to Myrtle Beach and took up golf.

His first wife, Mildred Geisler, died in 1997, and his second wife, Hazel McKnight Geisler, died in July.

Survivors include two stepchildren, Eugene "Duff" Field of Marcellus, N.Y., and Patricia Taylor of Brackney, Pa.