`=>` A sound wave is an example of a mechanical wave.

`=>` A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium. A mechanical wave requires an initial energy input. Once this initial energy is added, the wave travels through the medium until all its energy is transferred.

`=>` A mechanical wave is a wave that is not capable of transmitting its energy through a vacuum.

`=>` Sound waves are longitudinal waves.

`text(Longitudinal Wave:)`
Longitudinal waves are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of propagation of the wave.

`text(Sound Waves as Pressure Wave:)`
Since a sound wave consists of a repeating pattern of high-pressure and low-pressure regions moving through a medium, it is sometimes referred to as a pressure wave.

We should know about some terms related to sound waves before the discussion of musical instruments.

`=> text(Amplitude:)`
The magnitude of the maximum disturbance of particles in the medium on either side of the mean value is called the amplitude of the wave. It is usually represented by the letter A. Its SI unit is metre (m).

`=> text(Frequency:)`
The number of vibrations per unit time is called the frequency of the sound wave. It is represented by `f` or `nu`. Its SI unit is hertz (Hz).
`f=1/T`, where T = time period

`=> text(Wavelength:)`
The distance from crest to adjacent crest or from trough to adjacent trough or from any point on the wave medium to the adjacent corresponding point on the wave medium. The wavelength is usually represented by `lamda`. Its SI unit is metre (m).

`=> text(Pitch:)`
The pitch of a sound is determined by the rate of vibration, or frequency, of the sound wave. The pitch is simply the rate at which vibrations are produced. This is usually expressed as the number of Hz (hertz, or cycles per second).

`=> text(Interference:)`
Superposition of waves results in maximum and minimum of intensities such as in case of standing waves. This phenomenon is called as interference. Another type of superposition results in interference in time which is called as beats.

`=> text(Natural Frequency:)`
Natural frequency is the frequency at which a system tends to oscillate in the absence of any driving or damping force.

`=> text(Overtones:)`
An overtone is any frequency greater than the fundamental frequency of a sound.

`=> text(Fundamental Frequency and Harmonics:)`
The lowest resonant frequency of a vibrating object is called its fundamental frequency.
Most vibrating objects have more than one resonant frequency and those used in musical instruments typically vibrate at harmonics of the fundamental. A harmonic is defined as an integer (whole number) multiple of the fundamental frequency.
Each natural frequency that an object or instrument produces has its own characteristic vibrational mode or standing wave pattern. These patterns are only created within the object or instrument at specific frequencies of vibration; these frequencies are known as harmonic frequencies, or merely harmonics.

A musical instrument is an instrument created or adapted to make musical sounds. In principle, any object that produces sound can be a musical instrument—it is through purpose that the object becomes a musical instrument.

Throughout history, various methods of musical instrument classification have been used. Some of the most commonly used system are given below.

`text(Classification of Classical Instruments:)`

Instruments classified into four main groups-
1. Idiophones, such as the xylophone, which produce sound by vibrating themselves.
2. Membranophones, such as drums or kazoos, which produce sound by a vibrating membrane.
3. Chordophones, such as the piano or cello, which produce sound by vibrating strings.
4. Aerophones, such as the pipe organ or oboe, which produce sound by vibrating columns of air.

Instruments can be classified by their musical range in comparison with other instruments in the same family. These terms are named after singing voice classifications:
1. Soprano instruments: flute, clarinet, recorder, violin, trumpet, oboe, soprano saxophone
2. Alto instruments: alto flute, viola, French horn, natural horn, alto horn, alto saxophone, English horn
3. Tenor instruments: trombone, tenor saxophone
4. Baritone instruments: cello, baritone horn, bass clarinet, bassoon, baritone saxophone
5. Bass instruments: double bass, tuba, bass saxophone

In this chapter we will discuss some musical instruments-
Flute, Tabla, Harmonium, Sitar, Veena, Cymbals (Manjira), Ghatam, Noot (Mudpots), Kartal, Ektara, Jaltarang, Dholak etc.

The flute is a family of musical instruments in the aerophones group. It can be made by wood or metal.

`text(Construction:)`
As we can see in the figure a flute can be divided into three parts.
-Head Node
-Middle Node
-Foot Node

`text(Head Node-)` It is the part of flute which placed near to the mouth of flutist. It can be divided in three parts.
Mouthpiece
Flow Channel
Window

`text(Middle Node-)` This part consist holes which plays a major role to create music. Music creates according to the opening or closing holes.

`text(Foot Node-)` This part consist a big hole at the end and works to amplify sound.

`text(Working:)`
A flute produces sound when a stream of air directed across a hole in the instrument creates a vibration of air at the hole. The air stream across this hole excites the air contained in the cylindrical resonant cavity with the flute.
The flutist changes the pitch of the sound produced by opening and closing holes in the body of the instrument.
By varying the air pressure, a flutist can also change the pitch of a note by causing the air in the flute to resonate a harmonic rather than the fundamental frequency without opening or closing holes.

Dholak is a very popular folk drum of northern India, Pakistan and Bangladesh as well. It is barrel shaped, at times a cylindrical drum, with skins on both sides.

`text(Construction:)`
It consist mainly 3 parts - Shell, Rope and 2 animal skin surfaces.
The smaller surface of Dholak is made of goat skin for sharp notes and bigger surface is made of buffalo skin for low pitches which allows a combination of bass and treble with rhythmic high and low pitches.
The shell is made of wood.

`text(Working:)`
Generally the drum is played by palm and fingers by hitting on both surfaces. In some styles of playing an iron thumb ring is used to produce sound.

Tabla is most popular pair of drums in the Indian sub-continent. It is a pair which consists of a small right hand drum called "Dayan" and a larger metal one called "Bayan".
It belongs to membranophone family group.

`text(Construction:)`
A Tabla consist of two single headed barrel shaped small drums of slightly different size and shapes known as "dayan" and "bayan".
Dayan tabla is about 15 centimeter in diameter and 25 centimeter in height.
The bayan tabla is a bit bigger and deep kettle drum shaped about 20 centimeter in diameter and 25 centimeter in height.
Each is made of hollowed out wood or clay or brass, the dayan drum is laced with hoops, thongs and wooden dowels on its sides.
The dowels and hoops are used to tighten the tension of membrane.(see figure)

`text(Working:)`
The playing technique is complex and involves extensive use of the finger and palms in various configurations to create a wide variety of different sounds and rhythms reflected in mnemonic syllables.

It has freely moving reeds on which a patent was taken out in 1840 by the French instrument maker Alexandre Debain. In India harmonium was introduced by the missionaries who brought these percussion instrument in the nineteenth century.

Harmonium belongs to the family of aerophones.

`text(Construction:)`
A standard harmonium always has a wooden box known as body, handles to move the instrument, bellows, keys, stops(main and drone), reeds, reed board, coupler and scale changer.

`text(Working:)`
The instrument is a small, tabletop size, organ which has bellows at the back that is pumped by one hand while the other hand plays the keyboard.
A right handed player uses the right hand for the keys and left hand for playing the bellows.

Ghatam is replicates or conveys the meaning of the pot in Sanskrit. It is an ancient percussive instrument. Ghatam is known as Noot in Kashmir and Mudki in Rajasthan.

`text(Construction:)`
The Ghatam is a mud pan with a narrow mouth. From its mouth , it slopes outwards to form a ridge. Ghatam is made mainly of clay which is baked with brass or copper filling mixed with a samll amount of iron fillings.

`text(Working:)`
It can be positioned on the lap or a tabla-ring and is played with the fingers of both hands. The belly, neck and upper rim produce different tone colors.
A characteristics bass tone that can produce the results from beating the opening with the palm of one's hand.
It is the only instrument whose position is changed while playing.

It is basically a set of small cymbals.

`text(Construction:)`
It is made of two small copper plates tied together with a string.

`text(Working:)`
Hitting one against the other at its edge produces its high pitch sound.

Kartal is made of wooden blocks with holes for the fingers and circular copper plates pair of Kartals are played with both hands. It is a common percussion instrument.
It usually comes under the class of idiophones instrument.

`text(Construction:)`
A pair of wooden castanets with little bells attached to them was the earliest form of the kartal. Kartal comprises two similar shaped wooden pieces and is 8 to 12 inches long and 2 to 3 inches wooden pieces. One of the piece has a space for the thumb and the other to hold four fingers. It is palyed by same hand.

`text(Working:)`
Kartal are a pair of wooden blocks or frames with small metal jingles mounted in them. They are simply beaten together to provide a rhythmic sound.

Veena is a classical instrument basically plucked stringed instrument. Veena ranged from one string to one hundred, and were composed of many different materials like eagle bone, bamboo and wood & coconut shells.

`text(Construction:)`
The Saraswati Veena is nearly about 4 feet in length and consist of a big round resonator that is carved out of hollow log and jack wood.

It has a hollow neck (fret board ) that is lined with 24 brass frets, set in black wax on wooden tracks .At the tapering end of the neck is a tuning box that concludes in a downward curve and a beautiful carved dragons's head.
There are four main playing strings that are attached to the end of the resonator.

`text(Working:)`
The Veena is held tilted slightly away from the performer. One has to sit cross legged and place the Veena on the lap. A small gourd is placed on the left thigh of the player. The left arm of the Veena player comes curving from below the fret board and rests on the frets. The right hand is placed on the edge of the top plank in order to pluck the strings. The frets are played with the fingers of the left hand while the right is for plucking the strings. The lower string are played using the little finger.

Thea Ektara has a spherical resonator made of dried pumpkin, wood or coconut to which a split bamboo cane is attached as a neck. Into an opening at the bottom of the resonator a piece of leather is set and to this string is attached.

The string runs through the inside of the spherical resonator and between the forks of the bamboo cane up to the top end of the neck and is wrapped around a peg there.

The string of the Ektara is plucked with one finger, the pitch can be changed continually downwards by more and more pressing the two halves of the neck together

The Jaltarang is a percussion musical instrument. It is also known as a wave instrument.

It consists of a set of ceramic bowls which are placed in a semi circle. Each bowl is filled with varying quantities of water and music is created when the bowls are beaten with beaters or two cane sticks.

By varying the quantity of water in each bowl different sounds can be created.