If a button accordion produces the same note when the bellows are pulled and pushed, the next question is whether it can play every note of the chromatic scale or only the notes of one or more diatonic scales.
♢ Chromatic button accordions are basically equivalent to piano accordions. Where button colours differ, white buttons represent the notes of C major and black buttons the additional chromatic notes.
The compact buttons require less space per octave, so an instrument of the same size can offer a wider range.
Several keyboard systems exist. The widespread B-system and C-system are both based on three rows. Additional rows repeat the first rows and make playing more comfortable.
The B-system can be recognised by three white buttons in the outer row. One of them is B (called H in German notation).
The B-system is also used on the Russian bayan. A typical feature is its raised treble keyboard: unlike a conventional accordion, the underside of the keyboard does not finish flush with the back of the instrument.
On the C-system only two adjacent buttons in the first row are white; one of them is C. The notes rise in semitone steps from the outside towards the inside. On the B-system the direction is reversed.
♢ A diatonic unisonoric button accordion is the Russian garmoshka, also known as garmon, garmonika or Tula accordion.
The treble side has two rows. Apart from the upper three buttons, they contain only notes of the C-major scale when the instrument is tuned in C.
On the bass side, two rows provide major and minor bass notes and chords; a third row contains all bass notes of C major.
