An accordion is a free reed aerophone instrument with bellows, but there are actually many different instruments within the accordion family, with diverse sounds for various playing styles and genres of music. Major categories include diatonic, chromatic, piano, and concertinas.
A diatonic accordion plays only the notes of a diatonic scale, with no accidentals. When most people think of a diatonic accordion, they are thinking of a single action “push-pull” (or bisonoric) accordion. The pitch of the note changes according to the direction the bellows are going. For example, holding down one key while the bellows are going out, you may play a C, and when you bring them in, you play a D. Usually there are rows of buttons on the right side corresponding to notes of a diatonic scale, and on the left side are bass buttons. However, within diatonic accordions there are many variations. Here are a few:
One-row: The German melodeon has one 10-button row as its (right) treble side and has two bass buttons (left), providing a total of 20 available notes.
Organetto: Th is Italian accordion has up to 24 treble buttons and 12 bass buttons, but most have two bass buttons and one row of 10 treble buttons.
Two-row: To increase range and compatibility with other instruments, this accordion has another row of treble but-tons, which can either be one half-tone or a perfect fourth above the first row. Th ere are also three-, four-, and five-row accordions, following a similar pattern.
Italian: This variation has two rows of treble buttons, with the second row a perfect fourth above the first. An additional partial third row may have five or six buttons of accidentals.
Helicon: Named after the helicon tuba, this accordion’s longer, wider bass reeds have a distinctive “tuba” sound.
F. Walter created the first chromatic accordion in the 1850’s when he rearranged the reeds of a three-row diatonic. Today, double-action chromatic accordions are the most common. All of the keys are a semi-tone apart, covering all the notes, including sharps and flats. Usually, the pitch stays the same when the bellows change direction. Chromatic accordions can range from 20 (right) treble keys and 12 (left) bass buttons to modern button accordions with six rows of treble buttons and 160 bass buttons. The chromatic button accordion is widely used in Russia, where it is called the bayan.
Piano accordions are chromatic accordions with a piano keyboard. With its standardized Stradella bass system, it be-came the first universal accordion, allowing accordionists to play any type or make of piano accordion without switching systems. This is probably why it became the most popular accordion in the US. A full-size piano accordion has 41 treble keys on the right and 120 bass buttons on the left.
Ranging from four to 12 sides, concertinas have distinctive shapes and two keyboards, one on each end of the instrument’s bellows. They are smaller than most accordions, allowing players to move around more freely. There are no fixed chords, and all of the buttons are individual notes.
English: Either hexagonal or octagonal in shape, the English concertina has four parallel rows of buttons and supports for the thumb and finger on each end. It usually has 48 keys, a range of three-and-one-half octaves, and was originally intended to play violin melodies.
German: Square-shaped and bisonoric, German concertinas are usually based on the diatonic accordion, with two rows on each side, each tuned a fifth higher.
Anglo-German (or Anglo): Combining the English concertina shape and German concertina note system, the Anglo concertina adds an extra row of buttons for accidentals, making it fully chromatic.
Duet: Enables the player to play a melody line in the right hand and accompaniment in the left. There are varied systems and key layouts.
Bandoneon: Based on the German concertina, it has 72 or more buttons for a larger range of notes, usually up to four-and-one-half octaves. It can be diatonic or chromatic, and is popular with South American tango orchestras.