The alto trombone is pitched in E flat (occasionally with a D or B flat rotary valve attachment) or F, a perfect fourth or fifth higher than the tenor trombone, and was commonly used from the 16th to the 18th centuries as the highest voice in the brass choir.

It declined in popularity from the early 19th century, when the trumpet acquired valves and trombones became an established section in the symphony orchestra, and it was replaced by a tenor trombone as the range of the parts can usually be covered by the tenor instrument. While some first trombonists have used the alto trombone as indicated, it was unfashionable from the mid-19th century to the late 20th and has only recently enjoyed something of a revival. 

As the slide is shorter, the positions are different from the tenor and bass trombone slide positions most players are familiar with. The tone of the alto is more brilliant than that of the tenor or bass trombone. The bore of an alto trombone is similar to that of a small tenor trombone – usually around 0.5 inch with a 6.5 or 7 inch bell. 

The alto trombone is primarily used in choral, orchestral and operatic settings.