The Harmonica

The harmonica, which is also called a French harp or mouth organ, belongs to the free reed family of wind instruments. It appears in musical styles around the world, with a strong presence in blues, American folk, classical, jazz, country, and rock. Players choose from several types, including diatonic, chromatic, tremolo, octave, orchestral, and bass models. The player directs air into or out of one or more holes along a mouthpiece using the lips and tongue. Behind each hole sits a chamber that holds at least one reed. The most widespread version is a diatonic Richter-tuned harmonica, which has ten air passages and twenty reeds and is often referred to as a blues harp.

Each reed is a flat, elongated spring, typically made from brass, stainless steel, or bronze. One end of the reed is fixed over a slot that acts as an airway. When the player’s breath makes the free end vibrate, the reed alternately blocks and unblocks that airway, producing sound. Reeds are tuned to specific pitches by adjusting their length, the weight near the free end, or the stiffness near the fixed end. Longer, heavier, or more flexible reeds create lower pitches; shorter, lighter, or stiffer reeds create higher pitches. On most modern harmonicas, a reed is mounted above or below its slot rather than flush with it. This setup makes the reed respond more easily to air that pushes it into the slot—a closing reed. Because blow and draw reeds react differently to air direction, both can sit in the same chamber without needing plastic or leather valves to block the nonplaying reed.

A key technique is bending, which lowers the pitch through adjustments in the player’s embouchure. On chromatic models (or any with wind-savers), bending an isolated reed is possible. On unvalved harmonicas like the diatonic, players can also lower or raise pitch—through overbends, overblows, or overdraws—by using pairs of reeds in the same chamber. These two-reed pitch changes involve the normally silent reed producing sound; for example, the blow reed sounds while the player draws.

The harmonica has three basic parts: the comb, the reed plates, and the cover plates.

The comb forms the main body and, when assembled with the reed plates, creates air chambers for the reeds. Its name likely comes from its resemblance to a hair comb. Traditionally made from wood, combs now also come in plastic (ABS) or metal, including titanium for high-end instruments. Some modern and experimental comb designs direct air in complex ways. Players disagree on whether comb material affects tone. Those who say no argue that the comb is too small and cannot vibrate freely enough to change the sound, unlike a piano soundboard or a violin top. Those who say yes trust their ears. Most agree that a smooth, airtight seal between the comb and reed plates greatly affects tone and playability. The main advantage of one material over another is durability. Wooden combs can absorb moisture from breath and tongue contact, causing them to expand slightly and become uncomfortable, then contract and lose airtightness. Various wood types and treatments try to reduce this problem. A more serious issue with wooden combs, especially in chromatic harmonicas with thin chamber dividers, is cracking over time as the comb expands and shrinks while held immobile by nails, leading to disabling leaks. Serious players often restore wood combs and seal leaks. Some players used to soak wooden-combed diatonics (without wind-savers) in water to make the comb swell slightly, hoping for a better seal. Modern wooden combs are less prone to swelling, but some players still dip their harmonicas in water for its effect on tone and ease of bending.

The reed plate holds several reeds in one housing. Reeds are usually brass, though steel, aluminum, and plastic appear occasionally. They are typically riveted to the plate, but welding or screwing is also used. Reeds fixed on the inner side of the plate (inside the comb’s air chamber) respond to blowing; those on the outer side respond to suction. Most harmonicas have reed plates screwed or bolted to the comb or to each other. A few brands still nail the plates. Some experimental models, like WWII-era all-American harmonicas, held the plates by tension. Bolted plates can be replaced individually, which is useful because reeds go out of tune over time, and some notes fail sooner than others. An exception to traditional design is the all-plastic harmonica created by Finn Magnus in the 1950s, where the reed and reed plate were molded from a single piece of plastic, with the comb also made of plastic and either molded or permanently glued together.

Cover plates sit over the reed plates and are usually made of metal.