Musical Instruments
 

A musical sound, or note, is produced when air vibrates a certain number of times each second.  These vibrations are called sound waves.  Sound waves must be contained in some way so that the performer can control the pitch, loudness, duration, and quality of the note.  Whatever contains the sound waves must also provide resonance--that is, it must amplify and prolong the sound so the note can be heard. 

The vocal cords produce musical sounds in the human voice.  These two small folds of tissue vibrate and create sound waves when air passes them from the lungs.  The throat and the cavities in the head provide the resonance needed for singing. 

Most musical instruments have a string, a reed (thin piece of wood or metal), or some other device that creates sound waves when set in motion.  Musical instruments can be grouped in five major classes.  These classes are (1) stringed instruments, (2) wind instruments, (3) percussion instruments, (4) keyboard instruments, and (5) electronic instruments. 

Stringed instruments produce notes when the player makes one or more strings vibrate.  There are two basic types of stringed instruments: (1) bowed stringed instruments and (2) plucked stringed instruments. 

Bowed stringed instruments are played by drawing a bow (a wooden rod with horsehair stretched from end to end) back and forth across the strings.  The friction (rubbing) of the bow on the strings produces vibrations that are amplified by the body of the instrument.  Most bowed instruments have four strings.  Each string is tuned to a different pitch.  To produce other pitches, the musician shortens the strings by pressing down on them with the fingers. This is called stopping. The main bowed instruments, in descending order of pitch and ascending order of size, are the violin, viola, violoncello or cello, and string bass.  These instruments form the heart of a symphony orchestra.  Violins in an orchestra are divided into first violins and second violins.  The first violins play higher-pitched parts of musical compositions than the second violins. 

Plucked stringed instruments are played by plucking the strings with the fingers or a pick or plectrum.  The guitar is the most common plucked stringed instrument.  It has 6 to 12 strings.  The harp, another important plucked instrument, has up to 47 strings.  Other plucked stringed instruments include the banjo, lute, lyre, mandolin, sitar, ukulele, and zither.  The strings of the violin and other bowed instruments also may be plucked to produce special effects.  This style of playing on a bowed instrument is called pizzicato. 

Wind instruments are played by using breath to vibrate air in a tube.  There are two chief types: (1) woodwind instruments and (2) brass instruments. 

Woodwind instruments are grouped together because, before the invention of the saxophone, they were all made of wood.  Today, many are made of metal or other materials.  In such woodwinds as recorders, the player blows into a mouthpiece.  In some other woodwinds, such as flutes and piccolos, the player blows across a hole in the side of the instrument.  Still other woodwinds, called reed instruments, have one or two reeds attached to the mouthpiece.  The reeds vibrate when the musician blows on them.  The clarinet and saxophone are the chief single-reed instruments.  Double-reed instruments include the bassoon, English horn and oboe. The player controls the pitch of a woodwind by placing the fingers on holes in the instrument or on keys that cover holes.  In this way, the player lengthens or shortens the column of air that vibrates inside the instrument.  The piccolo and flute have the highest pitches of the woodwinds.  The bassoon and contrabassoon have the lowest pitches. 

Brass instruments are played in a different way from that of woodwinds.  The player presses the lips against the instrument's mouthpiece so that they vibrate like reeds when the player blows.  By either tensing or relaxing the lips, the player produces different pitches.  With many brass instruments, the player can further control the pitch with valves that lengthen or shorten the tube in which the air column is made to vibrate. The chief brass instruments in an orchestra are the French horn, trumpet, trombone, and tuba.  The French horn and trumpet have high pitches, and the trombone and tuba have lower pitches.  The trombone has a slide instead of valves.  The performer pulls the slide in and out of the instrument to control the pitch.  Other brass instruments, including the baritone horn and sousaphone, are used in bands. 

Percussion instruments are sounded by shaking them or by hitting them with the hand, a stick, or a mallet.  Drums are the most common percussion instruments.  Most Western drums do not produce a range of pitches.  But kettledrums, also called timpani, can be tuned to various pitches by adjusting the tension of the drumheads.  Glockenspiels and xylophones have a series of metal or wooden bars that produce a range of pitches.  Other percussion instruments include castanets, cymbals, gongs, marimbas, and tambourines. 

Keyboard instruments have a series of keys connected by mechanical means to a device that produces notes.  The musician presses the keys to make sounds.  The best-known keyboard instruments are the piano, harpsichord, and pipe organ.  The keys on a piano activate small hammers that strike strings.  On a harpsichord, the keys control a mechanism that plucks strings.  Pressing a key on a pipe organ opens a pipe in which a column of air vibrates.  The player operates some pipes by pressing pedals with the feet. 

Electronic instruments include those that generate sounds by electricity and those that electronically amplify sounds produced by an instrument.  The most common electronic instrument is the electric guitar.  It makes louder and more varied notes than an ordinary guitar.  Electric guitars, electric pianos, and electronic organs are widely used in rock music.  A complex electronic instrument called a synthesizer is used to create original sounds or to imitate the sounds of other musical instruments.  Some synthesizers are operated by computer.