Betty O’Hara, 74, versatile jazz musician, singer and composer who co-founded a women’s jazz quintet, The Jazzbirds. O’Hara was considered a pioneer in the male-dominated world of jazz. Born in Earl Park, Ind., she began playing the trumpet at 9. She performed in the Hartford, Conn., symphony and other ensembles before moving to Southern California in 1960 with her husband, bass trombonist Barrett O’Hara. She worked as a studio musician, recording soundtracks for such prime-time television shows as “Hill Street Blues” and “Magnum P.I.” By the late 1970s she was a charter member of the big band that became Maiden Voyage. In the early 1980s she formed The Jazzbirds with trumpeter-flugelhornist Stacy Rowles. She could play trumpet, cornet, piccolo-trumpet, fluegelhorn, trombone, valve trombone and a mutant instrument called the double-bell euphonium. Her facility with brass instruments once prompted Times jazz critic Leonard Feather to note that “if it has valves, Betty O’Hara will play it.” Feather called her a “gently melodic player” and a singer of personal charm. She was featured at the Monterey Jazz Festival. O’Hara had suffered two strokes since 1998. On April 18 at Sherman Oaks Convalescent Hospital of complications of a stroke.