The Trombone is a relatively old musical instrument. It appears that almost no great change has been made to it during the past 450 years. The exception to this are some alterations to the bell and mouthpiece, which may reflect on the tastes of the different times regarding timbre and tone quality. Until the 19th century, the Trombone was the only instrument in the brass family which could produce the entire chromatic range.
The reason for this agility, is the fact that it is the only brass instrument which uses a slide instead of valves to lengthen its tube. This slide is made with the finest precision, with outer walls almost a quarter of a millimeter thick. When the slide is moved outwards, it lengthens the tube by semitones, thereby producing a new set of harmonic series in each of the seven different possible positions. In this manner, any tone can be produced without difficulty. One of the most humorous effects can be obtained by producing the sounds and simultaneously moving the slide, thus creating a beautiful glissando.
The Trombone is usually made of brass, chromium and nickel. It has a cylindrical tube, which is approximately two thirds of its length, and becomes conical as it approaches the bell (which has a diameter of approximately 18 cm.). The mouthpiece resembles the Trumpet's mouthpiece, but is slightly larger. The player holds the instrument with his left hand by the mouthpiece, firmly steadying it against his lips. With his right hand, he operates the slide.
The most commonly used sizes of Trombones in today's symphonic orchestra are the Tenor and Bass Trombones. There is also an Alto Trombone, which is pitched a perfect fifth above the Tenor Trombone. The Bass Trombone is pitched a perfect fifth below the Tenor.
Mutes are usually employed to lower the volume of tone, as well as to produce a rich variety of colors. A water key is used to drain the water which accumulates in the tube.
The Trombone has a relatively homogeneous tone quality throughout its range. In its lower register, the instrument can produce very soft sounds. When blown very forcefully, these tones become dramatic and quite powerful. The Trombone's medium register is nearest to the horn in tone quality. The tone becomes more brilliant and penetrating as it approaches the higher notes, and may suggest tension and excitement in the highest tones.
In the fourth movement of his Fifth Symphony, Beethoven calls for three Trombones: an Alto, a Tenor, and a Bass Trombone.
