American musician who—both independently and with his brother Jimmy (Dorsey, Jimmy)—led several of the most popular big bands of the swing era. He was also a highly respected and influential trombonist.

Both brothers received their first musical training from their father, a music teacher and marching band director. Tommy began his performance career on trumpet and trombone, eventually playing the trombone exclusively, though his trumpet playing was exceptional. As teenagers, they worked in several bands before forming their own combo, Dorsey's Novelty Six, in 1920. By 1922 the group, now known as Dorsey's Wild Canaries, had attained some prominence in the Baltimore, Md., area and was among the first jazz bands to be broadcast on radio. During this period the brothers also played (sometimes separately but usually together) in a variety of musical groups. In 1927 they began recording with a changing slate of musicians they dubbed the Dorsey Brothers Orchestra. They had a string of hits in the late 1920s and early '30s, often featuring vocalists such as Bing Crosby and his younger brother Bob.

After splitting with Jimmy in 1935, Tommy took over the remnants of the recently disbanded Joe Haymes Orchestra. Soon thereafter Tommy recorded "I'm Getting Sentimental Over You," which became his theme song and the source of his nickname, “The Sentimental Gentleman of Swing.”

Dorsey's big band played music that ranged from smooth dance tunes to hot swing; Dorsey had a small group, the Clambake Seven, for more intense jazz. Noted sidemen who played for Dorsey included trumpeters Bunny Berigan and Ziggy Elman, saxophonists Bud Freeman (Freeman, Bud) and Johnny Mince, guitarist Al Viola, pianist Joe Bushkin, and drummer Buddy Rich (Rich, Buddy). The band's outstanding arrangers included Paul Weston, Bill Finegan, and Sy Oliver (Oliver, Sy). Among their hit recordings were "Boogie Woogie," "The Dipsy Doodle," "Marie," "Song of India," "Opus One," and "On the Sunny Side of the Street." With its versatility and excellence, Tommy's was one of the most consistently popular bands of the swing era.

Singers were important in Dorsey's band from the start, and many early recordings featured the popular baritone Jack Leonard. But the crooner Dorsey hired in January 1940—a 24-year-old named Frank Sinatra (Sinatra, Frank)—was the band's main attraction for nearly three years. In later years, Sinatra acknowledged his debt to Dorsey and frequently cited him as his main musical influence in terms of phrasing and breath control. Classic Dorsey-Sinatra sides include "I'll Never Smile Again," "I'll Be Seeing You," "Oh! Look at Me Now," "East of the Sun," and "In the Blue of Evening."

Dorsey perfected a ballad style on the trombone, noted for seamless legato phrases and purity of tone. He earned high praise from critics and fellow musicians for his distinctive sound and accurate intonation. Noted jazz historian Gunther Schuller (Schuller, Gunther) stated: “Dorsey was clearly the creator and master of this smooth ‘singing' trombone style, so seemingly effortless, largely because of his flawless breath control.” Fine examples of Dorsey's trombone can be heard on such recordings as "If My Heart Could Only Talk," "Annie Laurie," "Tea for Two," and "Say It."