The Accordion: Bellows, Keys, Buttons, and Reeds

The accordion is an instrument that breathes. Two wooden boxes, joined by a folding bellows, push and pull air through a set of tiny metal tongues, and each tongue vibrates as the air rushes past. The player controls volume and expression mostly with the arm that works the bellows, while the fingers choose which tongues will speak.

The sound source: the free reed

The sound-producing element of the accordion is the free reed, a small strip of metal, usually brass or steel, fixed at one end over a rectangular slot in a plate. When air is forced through the slot, the strip swings in and out of it, chopping the airflow into rapid pulses. Repeated hundreds of times per second, those pulses are heard as a note.

The word "free" has a precise meaning: the strip passes through the slot without striking its edges, unlike the beating reed of a clarinet or saxophone, which slaps against the mouthpiece. As a result, the pitch is set mainly by the size and mass of the strip itself. Long, thick reeds give low notes; short, thin ones give high notes. The same principle appears in the harmonica and the reed organ, and it has a very old ancestor in the Chinese sheng, a mouth organ of pipes fitted with free reeds.

Because pitch depends on the reed, the accordion does not need a resonating tube for every note, which is why it can be built small and portable. For more on how vibrating bodies turn into sound, see how instruments produce sound.

Bellows, valves, and the hand that moves the air

The bellows is the engine of the instrument. It is made of folds of cardboard and cloth, reinforced at the corners with metal protectors, joined by flexible strips and sealed so that no air leaks. Opening it creates suction inside the instrument; closing it creates pressure. The reeds sound in both directions, so the player can shape long phrases without stopping to "take a breath."

Each reed sits in its own chamber and is protected by a valve, a flap of thin leather or plastic glued on the side opposite the slot where the reed vibrates. The valve works like a small door: it lets air through in one direction and shuts in the other, so that each reed speaks only when the pressure is moving the right way. Without valves, every reed in a chamber would respond at once, on both the push and the pull.

Players also have an air button or lever that opens the bellows without sounding any notes. It is used to reposition the instrument in the middle of a passage, for example when the bellows are nearly fully closed and the music keeps going.

The right hand: keys or buttons

The right hand plays the melody. On one of the most widespread types, the piano accordion, the keyboard resembles a piano's, with white and black keys in a row. Depending on the model, it covers anywhere from two to more than three octaves. Each key opens a passage that lets air reach the matching reeds.

On the chromatic button accordion, the right hand works rows of round buttons laid out so that neighboring notes sit on diagonals. Instead of one long row, the layout allows long scales to be played with finger patterns that repeat in any key. Several button systems exist, and each regional tradition has its favorite.

For a comparison with other instruments played from a keyboard, there is an overview in keyboard instruments: mechanisms and differences.

The left hand: basses and chords

The left hand is held under a strap and works buttons on the bass side. On the system most common on piano accordions, known as the Stradella bass, the buttons are organized in rows that follow the circle of fifths. One row provides single bass notes; the neighboring row provides ready-made major chords, another minor chords, and others seventh chords. With a single finger, the player sounds a full chord.

This arrangement is practical for dance music and accompaniment, because bass and harmony are within reach of the same hand. Concert models, called free-bass accordions, offer individual notes on the left side, which opens up classical and polyphonic repertoire to the instrument.

The number of basses, such as 12, 48, 80, or 120, indicates the size of the left-hand button set and is used in the trade to classify the size of an accordion. A 120-bass instrument is the standard full-size model; smaller ones are lighter and better suited to children or to players who want portability.

Registers, voices, and the full sound

Each note on an accordion can have more than one reed tuned in a chorus. Usually these reeds come in pairs: one tuned exactly to the note, another slightly above or below it. The small difference in frequency creates beats, a fluctuation in loudness that gives the sound a shimmering brightness. This is the so-called musette tuning, closely associated with French café and dance-hall music.

Registers are switches, usually on the upper part of the right-hand side, that turn sets of reeds on or off. With them, the player moves between a discreet, single-voice sound and a rich sound with several voices and doubled octaves. It is comparable to the stops of an organ, which change the tone color without changing the note played. To understand why combining voices changes the color of the sound, read what determines an instrument's timbre.

Diatonic and chromatic

The diatonic accordion offers, in each row, the notes of a seven-note scale, and each button sounds different notes on the push and the pull of the bellows. The result is a compact instrument, ideal for traditional music in a few keys. Small button boxes and many popular folk models follow this principle. Changing key usually requires another instrument, or another row.

The chromatic accordion has all twelve notes of the scale and, in general, sounds the same note in both directions of the bellows. It is the standard for piano accordions and for concert button accordions. Its versatility allows playing in any key, but the instrument is heavier and more complex.

The bandoneon, a close relative of the accordion, was developed in Germany in the nineteenth century and became inseparable from tango in the River Plate region. It is also a bellows-driven free-reed instrument, but it has buttons on both sides and a character of its own, more cutting than that of the ordinary accordion.

Origins in brief

A patent for an instrument called the Accordion, with the name credited to Cyrill Demian, was registered in Vienna in 1829. It had buttons that sounded a whole chord on the left side and a few notes on the right. From there the design evolved over the nineteenth century, with the addition of the piano keyboard, individual basses, and the chromatic system. The accordion spread through dance music, street music, church music, and eventually the concert hall.

What to listen for

Once you know how the accordion works, you can hear it in the music. Listen for the small beating between paired reeds in a musette sound, for the slight change of color when the bellows reverse direction on a diatonic instrument, and for the way a skilled player hides the reversal entirely so the line seems to flow without a seam. Notice also how the left hand alternates a bass note with a chord, a pattern that gives so much folk and dance music its steady lilt.

Where to go from here

If you get the chance to try an accordion, start with the bellows: practice opening and closing while keeping the volume constant, because control of the air is what separates a clean sound from a jerky one. If you are choosing a model, compare weight, number of basses, and the type of right-hand layout before deciding, and see the guide on choosing your first instrument. To check what you have learned about free reeds, bellows, and keyboards, test your knowledge in the quiz.