One chamber holds both a blow reed and a draw reed
The harmonica—also French harp or mouth organ—is a free-reed pocket orchestra for blues, folk, jazz, country, and rock. On a typical ten-hole diatonic “blues harp,” twenty reeds share chambers so exhaling and inhaling speak different notes without leather valves blocking the idle spring.
Lips and tongue aim air through mouthpiece holes into comb chambers; each brass, steel, or bronze reed is a flat spring fixed over a slot, alternately sealing and opening as it vibrates. Longer, heavier, or more flexible reeds sound lower; shorter, lighter, stiffer ones sound higher. Mounting a reed above or below its slot makes it answer best to air that first pushes it closed—so a blow reed and draw reed can share one cell and play separately. Bending lowers pitch via embouchure; on unvalved diatonics, overblows and overdraws even recruit the normally silent “opening” reed to raise pitch.
Comb (wood, ABS plastic, or metal, even titanium), reed plates, and cover plates form the kit. Players argue whether comb material colours tone; fewer dispute that smooth, airtight mating shapes response. Wooden combs can swell with breath, then crack under nails—especially thin chromatic dividers—so serious players seal leaks; some still dip diatonics in water for bend feel. Reed plates usually bolt on for replacement as notes fatigue; Finn Magnus’s 1950s all-plastic moulded harps were a rare one-piece exception. Chromatics add button slides (or rare lever flaps) so one 12-, 14-, or 16-hole instrument covers every key.
Since the 1950s, Little Walter cupped a taxi-dispatcher “Bullet” mic into tube amps for punchy, sax-like “Mississippi saxophone” grit; folk players often prefer clean vocal mics such as a Shure SM58. Neck racks free the hands for guitar—wire-hanger ancestors still echo in Dylan and Springsteen stages. From brass springs to overdrive pedals, the reed’s simple block-and-unblock remains the whole machine.
Source: Harmonica
