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= Harmonica = The harmonica is a handheld rectangular free-reed wind instrument, most notably used in blues, jazz, country, and rock music. It is played by using the mouth to move air into or out of one or more of the holes along a mouthpiece into evenly spaced air channels. When a player blows into a hole, one of the reeds vibrates and produces a note and when a player breathes in, the other reed in the hole vibrates, so each hole can produce two notes. The length and thickness of the reed determines the note that is heard. The harmonica contains three basic parts: the comb, reed plates, and cover plates.

History
The harmonica was first invented in China and was originally called a “Sheng”. The “Sheng” had bamboo reeds and was a prominent instrument in Asian traditional music. It was introduced to Europe in the late 18th century, where it was popularised and developed into the harmonica we know of today.

The modern-day harmonica was developed early in the 19th century in Europe, and the first harmonicas were manufactured in Germany. The most well-known harmonica company, Hohner, is still based in Germany. The harmonica became a popular instrument due to it’s cheap and small nature, as it was very easy to carry around. There are many types of harmonicas (chromatic, diatonic, tremolo-tuned, orchestra, chenggong, and pitch), but the most widely used harmonica is the diatonic.

Comb
The comb is the harmonica’s main body, and forms air chambers for the reeds when assembled with the reed plates. Each chamber contains at least one flat, elongated spring called a reed made out of brass, stainless steel, or bronze, which is secured at one end over a slot that serves as an airway.

Cover Plate
Cover plates cover the reed plates, and can be made of metal, wood or plastic. Unlike the comb, in which there is debate as to whether the comb surface affect tone and playability, the cover plates do project sound, therefore determine the tonal quality of the harmonica.

Reed
The reed is the active element of the harmonica. Each reed is pre-tuned to individual pitches by changing a reed’s length, weight near its free end, or the stiffness near its fixed end. The reed is activated by air flowing across it, and it vibrates at a frequency near its natural frequency. This frequency is determined by the mass and stiffness of the reed and its associated acousitc system. The vibrating reed causes a periodic fluctuation which produces sound. The reed plate vibrates minimally when the natural note is played and acts as the opening reed. The frequency of vibrationg of the opening reed is primarily determined by the closing reed.

Shorter, lighter, and stiffer reeds produce higher-pitched sounds, and longer, heavier, and less stiff reeds produce deeper, lower sounds. In most modern harmonicas, a reed is fixed above or below its slot, rather than in the plane of the slot, which allows for it to respond more easily to air flowing in the direction that would initially push it into the slot, as with a closing reed. This difference in response to air direction allows for inclusion of both a blow reed and a draw reed in the same air chamber and allows for players to play them separately without relying on flaps of plastic or leather to block the nonplaying reed. Blowing into hole 1 vibrates and sounds the 1 blow reed, which would be C on a C harmonica, and inhaling on the same hole will vibrate and sound the 1 draw reed, which would be D on a C harmonica.

Free Reeds
A free reed is a small strip of material fixed at one end but set in or over a slot that is fractionally wider than the reed itself. Because of this, when pressure or suction is applied, the reed is able to swing freely through the slot to create a vibrating column of air which produces sound. The tongue of the reed can be either rectangular or triangular. It usually lies flush with the reed plate, and usually responds to both blowing and drawing of air. Free reeds must be connected to an appropriate resonator to produce sound, and the pitch of the reed depends on both the natural pitch of the reed, and the size and shape of the resonating chamber. The resulting sound is from the column of air set into motion by the reed rather than from the reed itself.

Diatonic Harmonica
The 10-hole diatonic harmonica is the most widely used type of harmonica, and it has a playing range of 3 full octaves and 22 diatonic tones. Each hole has 2 reeds, 1 for the inhale and 1 for the exhale. Therefore, because there are only 20 reeds and 1 tone is repeated, there are 3 "missing" natural tones. The diatonic harmonica arranges reeds so that each of the 3 octaves are played differently. For most of 2 octaves, the inhale note for the first 6 holes is in a higher pitch than the corresponding exhale note. For these 6 holes, it is the inhale note that can be bent. For the remaining 4 holes. the exhale note is higher in pitch, therefore is the one that can be bent.

The 10-hole diatonic harmonica is designed to play in a specific key, however, techniques such as overblowing and note-bending while playing in alternate positions allows players to play a diatonic harmonica in different keys.

In Blues music, players often perform in a “cross harp” or “second position” in which they play a harmonica that is tuned to a perfect fourth below the key of the written music. For example, if a song is written in the key of C, an F harmonica will be used. Many blues songs use notes of a pentatonic scale, and to compliment a pentatonic C scale, a player can play a G-tuned harmonica to complement it.

Bending
Bending is a technique that allows players to play semi-chromatically on a diatonic harmonica. A player can bend the pitch of a higher tuned reed down to the pitch of the lower tuned reed in any hole. On a diatonic harmonica, holes 1 through 6 inhale notes can be bent, while holes 7 through 10 exhale notes can be bent. As a general rule of thumb, it is the pitch higher note of the hole that can be bent down to a semitone above the lower note of the corresponding hole.

A large embouchure produces the best tone, with the jaw slightly dropped, throat open, soft palate raised, and tongue lowered. This embouchure creates a large and resonant chamber for tone production. This large embouchure allows the resonant pitch of the mouth, dictated by the volume of the oral cavity, to be lower than the pitch of any reed we play on the harmonica and their respective bends.

Using hole 4 on a C harmonica for example, the inhale note produces the sound at pitch D. As bending is performed, the constriction point moves back in the mouth and the pitch of the anterior chamber is lowered which results in the D note lowering in pitch. The exhale reed becomes tuned to C, a whole step lower than the draw reed. As bending lowers the D note of the inhale reed, the C reed becomes excited and vibrates. As a player continues the pitch-lowering process via bending, pitch production almost entirely transfers to the exhale reed.