Auxiliary percussion — sometimes referred to as ancillary percussion, toys, or sound effects — includes many of the smaller percussion instruments and those particularly that are not standard to the orchestra. Using the standard categories for typing percussion instruments, we can say that most auxiliary percussion instruments are either aerophones — instruments that create sound using air — or idiophones — instruments that create sound through the material they are made of, not through the application of an external sound-making tool, like a bow or a reed.
Auxiliary percussion aerophones include sirens and whistles. This set of instrument primarily adapts sounds from the “real world” to the orchestral environment. Some are based on warning sounds. Whistles may be made of plastic, wood, or metal. Some whistles are built for a single pitch, while others have multiple pitches.
The siren is a small boat warning signal in which the pitch rises and falls. There are also realistic sounding tugboat and locomotive whistles among the auxiliary percussion, which are recognizable as the sound that we write as "choo choo" in children’s books.
A wide range of bird whistles also reside in the category of auxiliary percussion. These include cuckoo, dove and pigeon, nightingale, jay and magpie, and warbler. And then there is the samba whistle, sometimes called a carnival whistle—an important element of Brazilian music and having up to three tones.
The idiophones included in auxiliary percussion are varied and we will consider three main groups. Percussion idiophones produce sound when struck with a mallet or beater. This group includes Chinese or Korean temple blocks, wooden chambers that characteristically come in sets of five, pitched from high to low; the triangle, a metal instrument in a triangle shape, suspended and struck with a metal beater; and woodblocks, hollowed blocks of wood with a slit opening, often in sets of three pitched high, medium, and low. Also included are the brake drum, a piece of an automobile that may be played with drum sticks, and the thunder sheet, which may be either beaten or shaken to produce a sound like a thunderstorm.
A second set of idiophones included in the auxiliary percussion is the scraped idiophones. This group features the ratchet, which produces a metallic clicking sound when its handle is turned; the musical saw, a pitched instrument that is held between the knees and played with a violin bow; and sandpaper blocks, blocks of wood with sandpaper attached and rubbed together to make a scraping sound.
Finally, we may turn to the shaken idiophones. In this group of auxiliary percussion, we find, first of all, rattles and shakers – solid shapes filled with loose particles that make a sound by hitting against the sides and other particles. This group also includes sleigh bells, a set of bells attached to a cloth band, and the tambourine, which can be shaken to set the metal disks jangling. Interestingly enough, if the tambourine has a head, and it is struck to produce sound, it is then considered a membranophone because the tone is produced by setting the stretched membrane vibrating.