Extended diatonic accordions - two and a half rows.

Some 2 row diatonic accordions have a third row, or partial row of between 2 and up to 10 buttons of accidental notes. Depending on the number of buttons this makes the instrument chromatic in at least one octave, which is referred to here as semi-chromatic, or fully chromatic through two or three octaves, although usually requiring bellows reversals in most keys.

There is a bewildering array of different instruments, with differing numbers of buttons and different keyboard layouts even on the same number of buttons! The most common have between 4, 5 , 6 or 7 buttons on the extra row. There are even Irish system two and a half row accordions!

The arrangement of notes on the extra row is the key to the strength and weaknesses of the resulting layout. Some try to strengthen and optimise the home keys of the diatonic rows, perhaps by making them availabe in both directions of the bellows, for example. Others look to extend the chromatic range through more than one octave, or optimise playing outside the home keys. In fact, professional musicians often have the notes on the extra row personalised to suit their playing style or particular kind of music. Several examples of layouts can be found at Melodeon.net.

If you like bisonoric accordions but want to play any kind of music in any key with similar ease, much better chording, much smoother, easier bellows work with less reversals, and you are willing to learn new fingering patterns, you should think about getting an Atzarin instrument!