Stradella bass system

The name is from Stradella, a town and commune of the Oltrepò Pavese in the Province of Pavia in the northern Italian region of Lombardy, once an important center for the production of accordions.

[citation needed] Each bass note, and each pitch in a chord, is usually sounded simultaneously in multiple octaves.

Within this convention, the written octave for bass and chord notes is arbitrary.

[citation needed] Patterns can be played identically in any desired key, changing only the starting position.

This is because, unlike a piano keyboard, the Stradella layout is isomorphic—meaning that a given sequence/combination of notes is played with the same relative finger positions and motions in any key.

A recommended fingering for harmonic minor:[7] Melodic minor (different ascending and descending): Larger and more expensive accordions may have as many as nine register switches on the bass side, controlling which reed ranks play and thus the octaves and voicing of the bass notes and chords, similar in concept to the treble register switches on the keyboard side.