The instrument is sometimes considered a "one-man-band", as it needs no accompanying instrument; the performer normally plays the melody on buttons or keys on the right-hand manual, and the accompaniment—consisting of bass and pre-set chord buttons—on the left-hand manual.
It is often used in folk music in Europe, North America, Russia, and South America. It is commonly associated with busking. Some popular music acts also make use of the instrument. Additionally, the accordion is sometimes used in both solo and orchestra performances of classical music.
The oldest name for this group of instruments is actually "harmonika". It comes as a mixture of "aer", "monos" and "cassa", the first two words being Greek and the last Italian. They mean "air", "unit" and "box", describing the instrument. Today, native versions of the name "accordion" are more often used, which is a reference to the type of accordion patented by Cyrill Demian, which concerned "automatically coupled chords on the bass side.
As such, the boundaries of what defines an accordion are perceivably broad.
The size and weight of an accordion varies depending on its type, layout and playing range, which can be as small as to have only two rows of basses and a single octave on the right-hand manual, for children, to the standard 120 bass accordion and through to large and heavy 160 bass button free-bass converter models.
Between the right- and left-hand manuals is a bellows, which is made from pleated layers of cloth and cardboard, with added leather and metal. It is used to create pressure and vacuum, driving air across the internal reeds and producing sound by their vibration, applied pressure increasing the volume. Similar to a violin's bow, the production of sound in an accordion is in direct proportion to the motion of the player. This makes the bellows the primary means of articulation.
Different systems are also in use for the left-hand manual, which is normally used for playing the accompaniment. These almost always use distinct bass buttons and often have concave buttons to help the player navigate the layout despite not being able to see the buttons while playing. Here, there are two general categories:
Inside the accordion are the reeds that generate the instrument tones. These are organized in different sounding "ranks", which can be further combined into producing differing timbres. All but the smaller accordions are equipped with switches that control which combination of reed ranks can be brought into operation, organized from high to low registers. Each register stop enables different sound timbres. See the accordion reed ranks & switches article for further explanation and audio samples.
All but the very small accordions usually have treble switches; the larger and more expensive accordions often also have bass switches.
Various hybrid accordions have been created between instruments of different buttonboards and actions. Many remain curiosities, only a few have remained in use. For example:
The accordion's basic form is believed to have been invented in Berlin in 1822 by Christian Friedrich Ludwig Buschmann, although one instrument has been recently discovered that appears to have been built in 1816 or earlier by Friedrich Lohner of Nürnberg in the German State of Bavaria.
The accordion is one of several European inventions of the early 19th century that used free reeds driven by a bellows. An instrument called accordion was first patented in 1829 by Cyrill Demian in Vienna. Demian's instrument bore little resemblance to modern instruments; it only had a left hand buttonboard, with the right hand simply operating the bellows. One key feature for which Demian sought the patent was the sounding of an entire chord by depressing one key. His instrument also could sound two different chords with the same key; one for each bellows direction (a bisonoric action).
At that time in Vienna, mouth harmonicas with "Kanzellen" (chambers) had already been available for many years, along with bigger instruments driven by hand bellows. The diatonic key arrangement was also already in use on mouth-blown instruments. Demian's patent thus covered an accompanying instrument: an accordion played with the left hand, opposite to the way that contemporary chromatic hand harmonicas were played, small and light enough to for travelers to take with them and use to accompany singing. The patent also described instruments with both bass and treble sections, although Demian preferred the bass-only instrument owing to its cost and weight advantages.
The musician Adolph Müller described a great variety of instruments in his 1833 book, Schule für Accordion. At the time, Vienna and London had a close musical relationship, with musicians often performing in both cities in the same year, so it is possible that Wheatstone was aware of this type of instrument and may have used them to put his key-arrangement ideas into practice.
Jeune's flutina resembles Wheatstone's concertina in internal construction and tone color, but it appears to complement Demian's accordion functionally. The flutina is a one-sided bisonoric melody-only instrument whose keys are operated with the right hand while the bellows is operated with the left. When the two instruments are combined, the result is quite similar to diatonic button accordions still manufactured today.
Further innovations followed and continue to the present. Various buttonboard and keyboard systems have been developed, as well as voicings (the combination of multiple tones at different octaves), with mechanisms to switch between different voices during performance, and different methods of internal construction to improve tone, stability and durability.
Although the accordion is best known primarily as a folk instrument, it has been used with increasing frequency by classical composers. The earliest surviving concert piece written for the accordion is Thême varié très brillant pour accordéon methode Reisner, written in 1836 by Miss Louise Reisner of Paris, an accordionist and amateur composer.
The Russian composer, Piotr Ilyitch Tchaikovsky, included four optional single-action diatonic accordions in his Orchestral Suite No. 2 in C Major, op. 53 (1883), simply to add a little color to the third movement: Scherzo burlesque.
The Italian composer, Umberto Giordano, included the single-action diatonic accordion in his opera Fedora (1898). The accordionist appears on-stage—along with a folk-trio consisting of a piccolo player and triangle player—three times in the third act (which is set in Switzerland), to accompany a short and simple song which is sung by a little Savoyard (Alpine shepherd).
In 1915, the American composer, Charles Ives, included a chorus of diatonic accordions (or concertinas)—along with two pianos, celesta, harp, organ, zither and an optional theremin—in his Orchestral Set No. 2. The accordion part—written for the right-hand only—consists of eighteen measures at the very end of the eighteen-minute-long three-movement work. All the above works were written for the diatonic button accordion.
The first composer to write specifically for the chromatic accordion (able to play all 12 notes of the chromatic scale) was Paul Hindemith. In 1921 he included the harmonium in Kammermusik No. 1, a chamber work in four movements for twelve players, but later rewrote the harmonium part for accordion. Other German composers also wrote for the accordion.
In 1922 the Austrian composer, Alban Berg, included a short on-stage accordion part in his landmark opera Wozzeck, Op. 7. The instrument—marked Ziehharmonika bzw. Akkordeon in the score—appears only during the tavern garden (wirthausgarten) scene, along with an on-stage (Bühnenmusik) ensemble consisting of: two fiddles (violins tuned up a tone), one clarinet in C, one guitar and one bombardon in F (or bass tuba), to lend a touch of authenticity to the deutsche bier garten setting.
Other composers who wrote for the accordion during the first half of the 20th century were:
Despite being invented as early as 1912, the instrument did not really become popular until the mid-twentieth century; when it was "discovered" by classical accordionists. The Danish accordionist Mogens Ellegaard, regarded by many as the father of the avant-garde accordion movement, described his introduction to the new accordion:
Symphonic Fantasy and Allegro was premiered by the Danish Radio Symphony with the composer conducting. Ole Schmidt made the following comment about the work, "I hated accordion until I met Mogens Ellegaard. He made me decide to write an accordion concerto for him."
Other Danish composers soon followed Schmidt:
In Europe, free bass accordion performance has reached a very high level and the instrument is considered worthy of serious study in music conservatories . Modern and avant-garde composers such as Sofia Gubaidulina, Edison Denisov, Luciano Berio, Per Norgard, Arne Nordheim, Jindrich Feld, Franco Donatoni, Toshio Hosokawa, Mauricio Kagel, Patrick Nunn and Magnus Lindberg have written for the free bass accordion and the instrument is becoming more frequently integrated into new music chamber and improvisation groups.
In the United States, the free-bass accordion is heard occasionally. Beginning in the 1960s, competitive performance on the accordion of classical piano compositions, by the great masters of music, occurred. Although never mainstreamed in the larger musical scene, this convergence with traditional classical music propelled young accordionists to an ultimate involvement with classical music heretofore not experienced.
Within the United States, a number of instrumentalists have demonstrated the unique orchestral capabilities of the free bass accordion while performing at the nation's premier concert venues and encouraging contemporary composers to write for the instrument. Included among the leading orchestral artists was John Serry, Sr. A concert accordionist, soloist, composer, and arranger, Serry performed extensively in both symphonic orchestras and jazz ensembles as well as on live radio and television broadcasts. His refined poetic artistry gained respect for the free bass accordion as a serious concert instrument among prominent classical musicians and conductors of the early twentieth century.
Recently Guy Klucevsek has built a reputation on combining folk styles with classical forms and makes extensive use of the free bass. New York's William Schimmel, who composes and performs in many genres, is a leading exponent of the "quint" style free bass system and uses it extensively in tandem with the standard stradella system.
Sometimes, certain traditional music styles may even be tied to a certain type of accordion, like the Schrammel accordion for Schrammelmusik or the Trikitixa for Basque music. It would be hard to name one country in which the accordion did not play a significant role in its music tradition. It has even been idealized in literature.
The instrument was also used in the Disney song "Whale of a Tale" from 20,000 Leagues Under the Sea, as well as Donald Duck's song, "Quack Quack Quack". It was used in a Christmas setting for the song "Nuttin' for Christmas".
The best accordions are always hand-made, especially in the aspect of reeds; completely hand-made reeds have a far better tonal quality than even the best automatically-manufactured reeds. Some accordions have been modified by individuals striving to bring a more pure sound out of low-end instruments, such as the ones improved by Yutaka Usui, a Japanese-born craftsman.