Sackbut

A sackbut is an early form of the trombone used during the Renaissance and Baroque eras. A sackbut has the characteristic telescopic slide of a trombone, used to vary the length of the tube to change pitch, but is distinct from later trombones by its smaller, more cylindrically-proportioned bore, and its less-flared bell. Unlike the earlier slide trumpet from which it evolved, the sackbut possesses a U-shaped slide with two parallel sliding tubes, rather than just one.