Harmonicas are hand-held instruments in which you blow or suck air through small reeds to produce sound. Harmonicas, which belong to the mouth organ family and are also known as mouth harps, are considered a folk instrument because they are easy to learn and produce raw, emotional music. Harmonicas have been made of glass, rock, wood, and other materials in many cultures, but the body is usually made of metal or plastic, and the reeds are metal.
Harmonicas are one of the few instruments that can be played by both “blowing” (breathing out) and “drawing” (breathing in), with dramatically different results. Harmonicas are classified as free reed instruments because they remain stationary while being played. The harmonica, unlike a trumpet or saxophone, is played entirely with the lips, tongue, and breathing patterns, with no other buttons or keys to move or bend the air to change the pitch.
Harmonicas are also known as idiophones in the classification of musical instruments. This is because, unlike a string or a membranous drum, the sound is created by the reeds’ unique resonating characteristics. People do not tune reeds in the same way that string tension affects tone. Rather, selecting the right reeds and varying the pressure or form of the air blown across them produces a difference in harmonica sound.
A dozen or more pre-tuned reeds are suspended in the comb, a narrow chamber in the body of a harmonica. Exhaling or inhaling from one side of the chamber causes one or a few reeds to vibrate at the same time, producing interesting textural or harmonic sounds on the other side. The number of holes, and thus reeds, on a child’s harmonica can range from four to sixteen for a professional musician. To produce different sounds, square holes funnel air to two possible reeds of a pair, known as the “blow” and “draw” reeds.
Diatonic tuning is one of the most common harmonica tunings. This means the reeds play major scale notes without any flat or sharp notes in relation to the key note. The most common is a diatonic harmonica in which each note is played by a single reed, though other types combine two reeds to produce a major note.
Harmonicas have long been associated with blues, bluegrass, and country music in the United States. These types of music are intended to be performed spontaneously wherever people congregate. Because it is lightweight, inexpensive, easy to learn, and produces evocative music, the harmonica has become popular for these events.