Bandoneon is a type of concertina rather than a type of accordion.

Someone asked (way back) about Arab-tuned (24 notes to the octave) accordion. I used to play one in a Middle Eastern orchestra. They use the Western/12-note piano/keyboard layout, with selected notes retuned to half-flat or half-sharp notes. You might have E-half-flat on the black E flat key in one octave, whereas in the other octave it is E-flat. So, you just have to play your tune in whatever octave contains the necessary notes. They don't try to put in all of the theoretically possible 24 notes, they just select the more commonly needed ones like B half flat, A half flat...