Les Elgart, 77, trumpet player and big-band leader whose Les and Larry Elgart Orchestra recorded for Columbia Records. The elder Elgart began his career playing trumpet in bands headed by Bunny Berigan, Hal McIntyre, Charlie Spivak and Harry James. The Elgart brothers, who often headed individual bands, enjoyed their greatest popularity in the mid-1950s. Les Elgart, whose band had toured until his death and will now disband, was credited with writing the theme song for Dick Clark’s “American Bandstand” television program. On Saturday in Dallas of a heart attack.