Everyone knows that Tommy and Jimmy Dorsey each led an outstanding dance band during the swing era. And anyone who has seen The Fabulous Dorseys, the marginally accurate 1946 bio-pic about the brothers, knows that they were often the 'battling Dorseys", whose Irish temper drove them apart for many years. What is more important is that they were both superb musicians whose careers covered the almost the entire development of jazz from the early 1920s, when they both played with the Scranton Sirens as teenagers, until the beginnings of rock and roll. We will examine their careers as highly sought after side men in the 1920s; as co-leaders of the Dorsey Brothers Orchestra in 1934-35; as separate leaders of highly successful big bands; and finally as co-leaders during their final years of a band for television which featured, among others, a guest artist named Elvis Presley!