This is, without doubt, one of the richest section in the whole orchestra, including an unlimited number of different percussion instruments, which is still continually growing.
It is almost impossible to include all the percussion combinations used by every composer, as these are tireless in their continual search for new sound effects, to express their intentions in the realm of musical art.
Percussion instruments are usually defined as these instruments in which sound is produced by stricking one object with another. The sound is produced by the vibration of stretched membranes, such as calf-skins or different substitutes (as in the different drums), or by plates or bars which can be made of metal, wood or sonorous substitutes (as in xylophones or vibraphones).
Percussion instruments are usually subdivided into instruments which can produce definite pitches, such as timpani, tubular bells, xylophones and vibraphones, or instruments which produce a percussive noise like sound with indefinite pitch, such as the different drums, cymbals, triangles and many more.
Some of the percussion instruments are used to produce special effects, such as imitations or suggestions of extra-musical sounds. This group includes such instruments as wind-machines, whips, sirens, auto-horns, typewriters, and their only limit is the composer's imagination.
Although many of these instrruments are not of percussive nature, they are usually assigned to be played by the percussionist, so that they are included in this section. That is why one percussionist may have to play on several different instruments during a whole concert or even in one and the same composition.
Most of the percussion instruments are struck with a rich assortment of sticks or hammers. Some of them produce sounds by being shaken or rubbed.
Of course only a few of all these instruments appear with the same regularity in the symphonic orchestra. During the Baroque, Classical an Romantic periods, the most regular members of the symphonic orchestra were the timpani, with few exceptions, while the other percussion instruments were gradually added up to this day.
Percussion sounds are relatively short and die away faster than any of the other instruments of the symphonic orchestra, but some of them can produce extremely loud sounds, such as the cymbals and bass drum.
Here we shall include only those percussion instruments which are mostly used in the symphonic orchestras up to the Romantic period.
