How a Harmonica Works

The harmonica is often associated with the blues, but it is also used in jazz, country, rock, pop, and even classical music. It is classified as a free reed wind instrument (or aerophone).  So, let’s find out how a harmonica works. It is similar to the pipe organ and the accordion, only notes are selected by placing the mouth over the proper holes, rather than with a keyboard. Air flows past a metal reed (or reeds), usually made of brass or bronze, causing it to vibrate. Beyond that simple orientation, harmonica playing gets messier and more inventive. Experienced players can use techniques to force the instrument into producing notes it wasn’t built to make.

Harmonica Basics

Air enters the harmonica through its comb, which contains the air chambers that cover the reeds. The comb in a modern harmonica is often made of plastic or metal for durability, but on traditional instruments it was made of wood.

The sound of the harmonica comes from groups of reeds mounted on reed plates inside the instrument. Reeds are usually made of brass, but steel, aluminum, and plastic can also be used. Reeds located inside the comb’s air chamber respond to blowing and those on the outside respond to drawing (inhaling). The length of the reeds affects the pitch of the notes, with the longest (lowest) reeds to the left.

The part of the harmonica that houses the reed-plates is called the cover plate. Because the cover plate projects sound, variances in material—including metal, wood, or plastic—can determine the tonal quality of the instrument.

From Diatonic to Octave

The most common types of harmonica are diatonic, chromatic, tremolo, and octave. Each varies in terms of the range of notes it can play, as well as the style of music for which it is most suited.

The diatonic harmonica is common to blues and country and most contain 10 holes, with four middle holes comprising an octave, and holes on either side extending the scale. The chromatic harmonica can have 10, 12, or 16 holes, and also includes a button-controlled slider that allows the instrument to play all 12 notes of the chromatic scale. It’s the preferred harmonica for jazz and classical music.

Tremolo harmonicas are diatonic models with double holes, each with two reeds tuned to the same note, one slightly higher to create a tremolo (or vibrating) effect. It is popular in gospel, Latin, Asian, and international folk styles. Octave harmonicas also have double holes but the reeds are tuned one octave apart. Octave harmonicas are often used in Cajun, old time, and Irish music.

Bending and Crossharp

Developing your mouth in its approach to the instrument is one of the most difficult things for beginning players to learn. Once past the beginner phase, players learn tricks and techniques for changing pitch. Bending notes involves changing the shape of the mouth to produce sharps and flats.

Overblowing works on a similar principle, only with additional air forced out while blowing. Another technique called cross-harping allows players to play the harmonica in all 12 keys by utilizing bending techniques.