Any musical instrument that gets its basic sound from something other than a vibrating string (chordophones ), vibrating air column (aerophones), or electric signals (electrophones), is considered a percussion instrument, and the musician who specializes in playing this large variety of instruments is a percussionist. Percussion instruments are further classified as being either membranophones (drums) or idiophones. This is an introduction to the idiophones most commonly found in Western bands and orchestras.

Instruments are classified according to how their sound is produced. The Greek idios, meaning “one’s own”, refers to the fact that in idiophones, it is usually the body of the instrument itself that is producing the original vibrations (as opposed to chordophones, for example, in which the instrument’s body is just a resonator for the strings). In some idiophones (xylophones, for example), there is a whole series of potentially-vibrating pieces, but the main idea is still the same: the instrument (or piece of the instrument) is hung or held in some way so that it can vibrate freely when it is played.

Idiophones are further classified according to the action that causes the vibration. Idiophones are very common in music traditions throughout the world, and some categories (such as stamped or plucked idiophones) don't even have a representative in the typical Western ensemble. The categories that are represented in the typical band or orchestra include percussion, concussion, shaken, and scraped idiophones. Each of these categories includes many, many instruments from many musical traditions around the world. For each of these categories, you will find a list below of the instruments most commonly found in orchestras and bands.

Percussion idiophones are hit with slender, hard wooden sticks, or with beaters or mallets. Beaters and mallets have a long handle with a head that hits the instrument. They come in a great variety of sizes and materials. The head may be of hard wood or plastic, for example, or may be wrapped in a softer material. The type of mallet used affects the timbre of the sound produced, so the percussionist will choose specific mallets or beaters based on the sound wanted for a particular piece.

Concussion idiophones are played by clashing two of them together.

Shaken idiophones are played by being shaken. Although these are not as common as drums, percussion idiophones, and concussion idiophones, there are several shaken idiophones that show up often in orchestral and band music. Most of these are used as "color" instruments, to suggest a certain style or genre of music, or even, in the case of jingle bells, to suggest a season.

Scraped idiophones have a series of notches or ridges on them, and are played by scraping a stick or other implement across the notches. Scrapers are not very common in band or orchestral music, but a washboard (a ridged sheet of metal, from the North American "mountain music" tradition) or a guiro (a hollow, tubular wooden instrument, often shaped like a fish, from the Latin American tradition) may show up as a "color" instrument in concert or jazz band, to suggest a certain style or genre of music.

In fact, there are many, many percussion instruments, from the many idiophone categories, that are only an occasional part of the band and orchestral repertoire, including such things as sandpaper blocks, anvils, cowbells, even old-fashioned typewriters. Some of these unusual instruments are borrowed from other musical traditions; others are simply borrowed by composers from the sounds of everyday life. Although some percussionists specialize, becoming expert drummers or marimba-players, for example, every band and orchestral percussionist becomes adept at playing a multitude of interesting instruments, often switching between instruments many times during a single a piece of music.