Accordion
Right-hand keyboard systems

Different systems exist for the right-hand keyboard of an accordion, which is normally used for playing the melody (while it can also play chords). Some use a button layout arranged in one way or another, while others use a piano -style keyboard. Each system has different claimed benefits by those who prefer it. They are also used to define one accordion or another as a different "type":
startend:quotation, keywords:existence, punctuation:no_comma