The trombone is a brass instrument derived from the sackbut. Unlike most brass instruments today, the trombone doesn’t use valves to alter its fundamental note but a sliding mechanism instead. Using the slide, the player is able to alter the length of the tube and so change its fundamental pitch. There are seven recognised positions for the slide producing fundamental notes a semitone apart. The sound of the trombone has a noble quality and has also been used by composers for a dramatic effect.
In baroque times the trombone was confined to church music but is now standard in orchestral music, and military and brass bands. The trombone has also been used effectively used in jazz.
There are many sizes of trombone. These include the treble, alto, tenor, bass, tenor-bass (which is effectively a tenor trombone with a mechanism which allows for an extra length of tubing to be inserted, converting it to a bass trombone), and double-bass or contrabass. The tenor trombone is the most generally used today. It is notated in either tenor or bass clef, and has a range of about two and a half octaves.
There is also a valve trombone which has valves in place of a slide. The valve trombone is made in tenor and bass sizes.