The earliest accordions had a single row of ten buttons, each controlling a valve which controlled the air flow to a pair of metal reeds inside the instrument.  These ten pairs of reeds were tined to a diatonic (or Western major) scale, using a layout almost identical to the harmonica.  For each button, as with the harmonica, 2 different notes could be obtained: One note that played when the bellows were pulled open and a different, adjacent note in the scale would play when the bellows was pushed closed, reversing the air flow through the reeds, allowing for 20 notes through the ten pairs of reeds.  This "push-pull" arrangement provided a compact and simple system for playing diatonic melodies.  With 2 notes per buttons, 4 fingers could cover a complete 8 note octave.  The frequent reversal of bellows direction necessary to change notes added a rhythmic articulation of the notes very suitable for many types of dance tunes.  The simple two fingered bass arrangement allowed for minimal yet adequate accompaniment for most folk music.  These factors combined with rugged construction, a loud sound output and relative affordability made the diatonic accordion the most widely distributed and played accordion throughout almost every country in the world.  

One Row Diatonic Accordion 

Also known as the "German Style" diatonic accordion, it is the earliest accordion design still being made.  It features a single row of ten buttons, exposed valves and from 2 to 4 pull stops on top of the treble side of the instrument altering tone and register of a given note by controlling which reeds will sound.  It has only two bass accompaniment buttons. The four stop model remains popular amongst traditional French Canadian musicians in Quebec and Cajun musicians in Louisiana.  The Cajuns re-tune by filling some of the reeds to provide a sweeter harmony when certain combinations of notes are played together.  They also tune the middle sets of reeds in unison, without the tremolo found in most other accordions. 

The Organetto 

The organetto is a diatonic button accordion found in central and southern Italy.  It can have one or two rows of melody buttons and have from 2 to 12 bass buttons.  The most common version, known as "due botte," has 2 bass buttons (hence the name) and a single row of ten melody buttons.  It is often made with 3 or 4 extra buttons in a short second row to provide alternate fingerings.  The organetto usually has 3 reeds per note:  2 middle sets tremelo-tuned with a 3rd set tuned an octave lower and controlled by a pull stop. 

3-5 row "Helikon Bass" 

Also known as "tyrolean", "Alpine" or "Sterische Harmonica" (after the region in Austria) accordions, these are found, with slight variations, in Austria, Bohemia, Bavaria, Slovakia, and Slovenia.  They have from three to five diatonic rows of buttons.  Each row is tuned to a key a fourth above the previous row.  Named after the helikon, a type of European tuba, these instruments have the most powerful bass tone of all accordions, featuring from 11 to 19 bass buttons.  

Chromatic Button Accordion 

In 1850, in Vienna, the musical F. Walther re-arranged the reeds of a three row diatonic accordion to play a 46 note chromatic scale (a 12-note scale of all half steps).  Starting at the upper end of the keyboard, the notes progressed in a chromatic scale, diagonally across all three rows.  Unlike the diatonic button accordion, each button played the same note regardless of the bellows direction.  Walther's chromatic keyboard layout is one of the systems still in use.  Most modern chromatic button accordions have five rows of buttons.  They are still based on a three row chromatic pattern-the two additional rows duplicate the first two rows to provide alternative fingerings.  The advantage of a chromatic button keyboard is that only one fingering pattern is necessary to play all keys.  To change to another key, you simply shift your finger pattern across the keyboard and begin another note, as you might do on a guitar fingerboard.  Also, the hand can span 2-1/2 octaves as compared to a single octave on a piano accordion keyboard.  The chromatic button accordion is more widely used in Europe than the piano accordion.  Some larger chromatic button accordions with a "free-bass" system can play seven octaves or more. 

Piano Accordion 

The first piano accordion appeared in Paris in 1852; however, the size of the keys remained quite small.  The piano accordion was introduced to the United States by Pietro Deiro, Sr. in San Francisco in 1909.  Domestic manufacture of these instruments began shortly afterward, later becoming by far, the most popular system in the US.  Deiro is credited with popularizing the instrument and also enlarging the size of the keys to their current proportions, thus improving the playability of the instrument.  The piano accordion is manufactured with stradella or bass-free systems. 

Irish Accordion 

The melodeon, as the diatonic button accordion is known in Ireland and Great Britain, had a single row of ten buttons on the right hand keyboard and two bass accompaniment buttons for the left hand.  In order to render the ornamentation associated with the fiddle and bagpipes, and to play in additional keys, a second row of buttons was added.  This new second row of buttons was also diatonic, but was pitched a semi-tone higher or lower that the original row.  Instruments were made in key combinations such as: C/C#, C#/D, D/D#, and D/C#.  By the early 1950s the "B/C" system took hold because it allowed for a smoother and quicker style of playing.  The Irish accordion with its two rows tuned a semi tone apart is a member of a family of accordion keyboard systems known as the "semi-tone" keyboard.  The origin of these systems is somewhat untraceable as they appeared around the turn of the century all over the world.  By adding the second row of semi-tone away from the first row, it provided the missing sharps and flats, making the instrument fully chromatic, while preserving some of the push-pull technique and tonality of the diatomic accordion. 

2 and 3 Row Diatonic Button 

Known as "Vienna" or "Italian" style diatonic accordions.  They have 2 or 3 rows of buttons, each row tuned to a key a fourth higher than the previous row.  Some 2-row instruments have an additional 3rd row of 4 to 10 buttons of notes missing from the 2 diatonic rows.  These extra notes give the instrument a full, but awkward to finger, chromatic range.  There may be from 4 to 12 bass buttons.  The Tex-Mex and Mexican Norteno 3-row accordion players have developed a fast style of playing which involves crossing all the rows and using most of the notes that play when the bellows is pulled open.  Since all the accompaniment basses are not available on the pull stroke, most players do not play the basses at all, but rely on the other instruments of the conjunto group to provide the bass and chordal  accompaniment. 

Musette 

A four row button chromatic accordion popular in France.  It has three middle reeds tuned to produce a very strong tremolo which is evocative of the tone of the "musette" bagpipe.  Diatonic accordions were later replaced by the chromatic button accordions which are now known as "musette" accordions. 

BASS ACCOMPANIMENT SYSTEMS 

Diatonic Bass 

Diatonic accordions have one or two pairs of bass buttons on the left or bass side of the instrument for each row of buttons on the treble side.  Each pair consists of one button that produces a fundamental bass note and another button that produces a pre-set chord.  The tonic, or root, bass note and chord will sound when the bellows is pushed closed and the dominant bass note and chord will sound when the bellows is pulled open.  Since most chords are available in only one bellows direction, the accompaniment basses do not always match the requirements of the melody.  While the diatonic bass system is adequate for much folk music, there are occasions when the limitations of the system are apparent. 

Stradella Bass 

The "Stradella" bass system, often referred to as a "20 bass" system, is capable of providing accompaniment in all keys.  It features a row of fundamental and counter bass buttons and a row of buttons of major, minor, dominant 7th, and diminished chords.  It is possible but difficult to play limited single note bass melodies using the fundamental and counter bass row. 

Free-Bass 

The "free-bass" system, also known as "bassetti", consists of 3 or more rows of buttons, each playing a single note arranged in the same pattern as the treble keys in a button chromatic accordion.  While there are not pre-set chords available, the melodic possibilities are much expanded.  A five octave button chromatic accordion with a three octave free-bass system can have a total range (allowing for some overlap) of over seven octaves.  There are also "converter" systems that with the moving of a switch change a "stradella" bass system to a "free-bass" system.  There are also bass arrangements that have three rows of "free-bass" buttons next to a full "stradella" bass system. 

THE CONCERTINAS 

All concertinas have their keyboards set into the opposite ends of the instrument.  There are no preset chords available.  Each button plays a single note (occasionally two notes an octave apart) and notes are somewhat evenly distributed between left and right hands.  The instrument is held by some type of hand strap and often supported on the knees.  Some varieties of the instrument are as follows:  

English Concertina 

Octagonal or hexagonal ended instrument developed by Charles Wheatstone of London in the 1830s to play violin repertoire.  It has a range of three chromatic octaves.  Each button produces the same note regardless of the direction of the bellows; thereby it can easily produce smoothly flowing melodies. 

German Concertina 

Developed by Carl Friedrich Uhlig of Chemnitz, Saxony, Germany in 1834.  It is a square ended instrument based on the diatonic accordion push-pull system.  It divided the ten buttons into five buttons for another key a 5th higher was added above the first row. 

Anglo-German 

George Jones of London in 1850 built a hexagonal ended instrument using the diatonic German concertina fingering system to which he added another row of accidental notes making the instrument chromatic.  This instrument later became known as the "Anglo-chromatic" or simply "Anglo" system concertina.  

Bandoneon 

A large square-ended concertina.  It is based on the diatonic German system to which many additional buttons were added (for a total of 72 or more buttons) to provide a range of 4-1/2 chromatic octaves.  Each of these notes can be found in a pushing or pulling mode however, for each bellows direction, the buttons' location that will produce these notes is different.  Therefore, two completely different fingerings must be learned: one pattern for use when the bellows is opened, and another completely different pattern when the bellows is closed. 

Zulu or Sotho Concertina 

Also known in South Africa as a "squashbox" system.  These are inexpensive Italian and German made "German" system concertinas which have been retuned to a wide variety of tribal and individual scales and note arrangements used in South Africa traditional and popular music. 

ANCESTOR 

The lusheng, or reed pipe ("lu" = eed; "sheng" = pipe) belongs to a family of mouth organs that originated in South China and Southeast Asia and included the better known Lao khaen and the Chinese sheng.  These instruments are considered to have been in existence for over 2,000 years.  It is believed that it was a sheng that sent back to Paris in 1777 by a Jesuit missionary in China, that stimulated interest in experimenting with free reeds.  This resulted in the invention of various free reed instruments in the early 1800's such as the harmonica, reed organ and the instruments of the accordion family.