The middle part, bent double, slips into the outer parts, as in a telescope, so that by change of the vibrating length any tone within the compass of the instrument (which may be bass or tenor or alto or even, in rare instances, soprano) is commanded. It is the only member of the family of wind instruments whose scale, both diatonic and chromatic, is complete without the aid of keys or pistons, and which can slide from note to note as smoothly as the human voice or a violin. Softly blown, it has a rich and mellow sound, which becomes harsh and blatant when the tones are forced; used with discretion, its effect is often solemn and majestic.

Family of Instruments: The Trombone belongs to the family of Woodwind instruments. The earliest form of slide trumpet, which developed from the Sackbut instrument.