Piano Accordion

A piano accordion has piano-style keys on the treble side. This makes playing melodies relatively straightforward.

Most piano accordions use a Stradella bass system on the left-hand side. It provides simple bass-and-chord accompaniment. Each bass note is diagonally aligned with buttons for the corresponding major, minor and dominant seventh chords and, on some instruments, a diminished seventh chord.

For orientation, the C bass button is generally concave, while the other buttons are convex. The A-flat and E bass buttons are also often marked, for example with a textured surface.

A 48-bass accordion essentially provides all keys, although the dominant seventh and diminished seventh rows are incomplete. A 72-bass accordion provides the full system. On larger instruments, the outer chords are repeated to make movement from the top to the bottom easier; F-sharp major is equivalent to G-flat major, C-sharp major to D-flat major, and so on.

Some accordions allow individual notes to be played on the bass side using a free-bass system. Converter instruments can switch between individual notes and preset chords.