The harmonica, also French harp, blues harp, and mouth organ, is a free reed wind instrument used worldwide in nearly every musical genre, notably in blues, American folk music, jazz, country, and rock and roll. There are many types of harmonica, including diatonic, chromatic, tremolo, octave, orchestral, and bass versions. A harmonica is played by using the mouth (lips and/or tongue) to direct air into and out of one or more holes along a mouthpiece. Behind the holes are chambers containing at least one reed. A harmonica reed is a flat elongated spring typically made of brass or bronze, which is secured at one end over a slot that serves as an airway. When the free end is made to vibrate by the player's air, it alternately blocks and unblocks the airway to produce sound. Reeds are pre-tuned to individual pitches. Tuning may involve changing a reed's length, the weight near its free end, or the stiffness near its fixed end. Longer, heavier and springier reeds produce deeper, lower soun...