Snare drum in the context of "Orchestral percussion"

An orchestra (/ˈɔːrkɪstrə/ ; OR-ki-strə) is a large instrumental ensemble typical of classical music, which combines instruments from different families. There are typically four main sections of instruments:

• The string section, including the violin, viola, cello, and double bass
• The woodwind section, including the flute, oboe, clarinet, bassoon, and occasionally saxophone
• The brass section, including the French horn (commonly known as the "horn"), trumpet, trombone, cornet, and tuba, and sometimes euphonium
• The percussion section, including the timpani, snare drum, bass drum, cymbals, triangle, tambourine, tam-tam and mallet percussion instruments

Other instruments such as the piano, harpsichord, pipe organ, and celesta may sometimes appear in a fifth keyboard section or may stand alone as soloist instruments, as may the concert harp and, for performances of some modern compositions, electronic instruments, and guitars.

A percussion instrument is a musical instrument that is sounded by being struck or scraped by a beater including attached or enclosed beaters or rattles struck, scraped or rubbed by hand or struck against another similar instrument. Excluding zoomusicological instruments and the human voice, the percussion family is believed to include the oldest musical instruments. In spite of being a very common term to designate instruments, and to relate them to their players, the percussionists, percussion is not a systematic classificatory category of instruments, as described by the scientific field of organology. It is shown below that percussion instruments may belong to the organological classes of idiophone, membranophone, aerophone and chordophone.

The percussion section of an orchestra most commonly contains instruments such as the timpani, snare drum, bass drum, tambourine, belonging to the membranophones, and cymbals and triangle, which are idiophones. However, the section can also contain aerophones, such as whistles and sirens, or a blown conch shell. Percussive techniques can even be applied to the human body itself, as in body percussion. On the other hand, keyboard instruments, such as the celesta, are not normally part of the percussion section, but keyboard percussion instruments such as the glockenspiel and xylophone (which do not have piano keyboards) are included.

The percussion section is one of the main divisions of the orchestra and the concert band. It includes most percussion instruments and all unpitched instruments.

The percussion section is itself divided into three subsections:

The bass drum is a large drum that produces a note of low definite or indefinite pitch. The instrument is typically cylindrical, with the drum's diameter usually greater than its depth, with a struck head at both ends of the cylinder. The heads may be made of calfskin or plastic and there is normally a means of adjusting the tension, either by threaded taps or by strings. Bass drums are built in a variety of sizes, but size does not dictate the volume produced by the drum. The pitch and the sound can vary much with different sizes, but the size is also chosen based on convenience and aesthetics. Bass drums are percussion instruments that vary in size and are used in several musical genres. Three major types of bass drums can be distinguished.

• The type usually seen or heard in orchestral, ensemble or concert band music is the orchestral, or concert bass drum (in Italian: gran cassa, gran tamburo). It is the largest drum of the orchestra.
• The kick drum, a term for a bass drum associated with a drum kit, which is much smaller than the above-mentioned bass drum. It is struck with a beater attached to a pedal.
• The pitched bass drum, generally used in marching bands and drum corps, is tuned to a specific pitch and is usually played in a set of three to six drums.

In many forms of music, the bass drum is used to mark or keep time. The bass drum makes a low, boom sound when the mallet hits the drumhead. In marches, it is used to project tempo (marching bands historically march to the beat of the bass). A basic beat for rock and roll has the bass drum played on the first and third beats of bars in common time, with the snare drum on the second and fourth beats, called backbeats. In jazz, the bass drum can vary from almost entirely being a timekeeping medium to being a melodic voice in conjunction with the other parts of the set.

A drumhead or drum skin is a membrane stretched over one or both of the open ends of a drum. The drumhead is struck with sticks, mallets, or hands, so that it vibrates and the sound resonates through the drum.

Additionally outside of percussion instruments, drumheads are also used on some string instruments, most notably the banjo.

A drum beat or drum pattern is a rhythmic pattern, or repeated rhythm establishing the meter and groove through the pulse and subdivision, played on drum kits and other percussion instruments. As such a "beat" consists of multiple drum strokes occurring over multiple musical beats while the term "drum beat" may also refer to a single drum stroke which may occupy more or less time than the current pulse. Many drum beats define or are characteristic of specific music genres.

Many basic drum beats establish the pulse through alternating bass (on the on-beats) and snare drums (on the off-beats) strokes while establishing the subdivision on the ride cymbal (thus its name) or hi-hat: