Four different families of musical instruments are present in a symphony orchestra: strings, woodwinds, percussion and brass.
Strings (Violin, Viola, Cello, Double Bass, Harp)
The four major instruments in the string family, the violin, the viola, the cello and the double bass, are built the same way. The instruments are made of many pieces of wood which are glued together. The body of the instrument is hollow, thus becoming a resonating box for the sound. Four strings made of animal gut, nylon, or steel are wrapped around pegs at one end of the instrument and attached to a tailpiece at the other. They are stretched tightly across a bridge to produce their assigned pitches.
Woodwinds ( Piccolo, Flute, Oboe, English Horn, Clarinet, Bass Clarinet, Bassoon, Contrabassoon, Saxophone)
The three branches of the woodwind family have different sources of sound. Vibrations begin when air is blown across the top of an instrument, across a single reed, or across two reeds. Reeds are small pieces of cane.
Percussion (Snare Drum, Cymbals, Bass Drum, Tambourine, Triangle, Castanets, Guiro, Timpani, Glockenpiel, Xylophone, Chimes, Gong)
With a name that means, "the hitting of one body against another," instruments in the percussion family are played by being struck, shaken, or scraped. In the orchestra, the percussion section provides a variety of rhythms, textures and tone colors. Percussion instruments are classified as tuned or untuned. Tuned instruments play specific pitches or notes, just like the woodwind, brass and string instruments. Untuned instruments produce a sound with an indefinite pitch, like the sound of a hand knocking on a door.
Brass (Trumpet, Trombone, Tuba, French Horn)
Brass Family instruments produce their unique sound by the player buzzing his/her lips while blowing air through a cup- or funnel-shaped mouthpiece. To produce higher or lower pitches, the player adjusts the opening between his/her lips. The mouthpiece connects to a length of brass tubing ending in a bell. The shorter the tubing length, the smaller the instrument, and the higher the sound; and the longer the tubing length, the larger the instrument, and the lower the sound.
Keyboards (Piano, Harpsichord, Organ)
Keyboard instruments are often classified as percussion instruments because they play a rhythmic role in some music. however, most keyboard instruments are not true members of the percussion family because their sound is not produced by the vibration of a membrane or solid material.