Orchestral percussion are percussion instruments used in orchestras and concert bands mainly in classical music and related styles. The term can also refer to the department or study of performance on said instruments at a music school or conservatory. Generally within such a department, students are required to study all aspects of orchestral playing; with marimba, snare drum, and timpani being the three most basic areas of study. Orchestral percussion usually does not include drum set studies.
Gongs and tam-tams are easily confused with one another. A gong, generally, is a large hung cymbal with a nipple. As such, they're usually known as nipple gongs. This nipple is a small dome in the centre of the cymbal that produces a single note when struck with a soft beater. Conversely, a tam-tam has no nipple, and so has a flat central area. When this cymbal is struck with a beater (most usually a soft beater), it produces a myriad of sounds with no single overruling note.
One can distinguish the two by ear by following a simple method. A gong sounds like a slightly muffled church bell, producing a soft but clear note, whereas the tam-tam sounds much more like a large metal object being struck by a hard material.
Mallet percussion (also known as keyboard or tuned percussion) is the general name given to the pitched percussion family. The name is a slight misnomer, in that almost every percussion instrument is struck with some type of mallet or stick. With the exception of the marimba, almost every other keyboard instrument has been used widely in an orchestral setting.
There are many extremely common and well-known excerpts for most of the mallet instruments. Gershwin's Porgy and Bess remains the most requested xylophone excerpt at auditions, with Copland's Appalachian Spring, Kodály's Háry János Suite, and Kabalevsky's Colas Breugnon being other common choices, although the list is practically endless.