I want to buy an accordion with 48 basses. I googled and found there are two different numbers treble keys, 26 and 34. My question is: is 26-treble key okay to play most songs as good as 34-treble key? Or there is a quite big difference between them? Thanks. Steve
34 keys already tends to be quite limited: it is a range of less than 3 octaves (which would be 37 keys). With 48 basses, you are confined to keys harmonically close to C major (and playing with other people may cause you to run out of basses pretty fast, particular in minor modes) which limits your starting positions, and once you start playing more than one note, a second voice will easily stray a sixth from the main melody, leaving a rather confined space to work with.
Regarding the workable range, chromatic button accordions tend to squeeze quite a bit more range into the same space particularly of small accordions but require more practice until you can play utilising simple scales (the advantage being that there are just 3 scales with regard to fingering compared to the 12 scales on a piano accordion; but at least when you are playing alone, you can avoid most of those scales on the piano accordion or postpone learning them for later).
Accordion literature tends to be playable mostly on 37 keys (typical for 96 basses) but sometimes wanting 41. Of course, that's not small instrument stuff. If you are playing simple melodies written for other instruments, one reference point may be the lowest note of a violin (which is a standard folk instrument), G3. You want to have that on your accordion keyboard. A 34-key accordion has it (typically starting at F3), a 26-key accordion hasn't (typically starting at B3).
It also rather depends what kind of music you’re planning on playing. If you’re playing folk music a 34 key will do you proud, because the music fits within that compass; they are also popular amongst Morris musicians because they are lighter to carry around. If you’re playing classical or jazz, the wider range the better as every 12 keys gives you another octave.