Family of Accordions

Piano Accordion

Right hand uses piano‑style keys
Left hand uses Stradella or free‑bass buttons
Most common in Western music, jazz, pop, and classical.

Chromatic Button Accordion (CBA)

Right hand uses chromatic button rows
Available in B‑system or C‑system layouts
Favored in classical, Balkan, Russian, and French traditions.

Diatonic Button Accordion (DBA)

Right hand tuned to specific keys
Different notes on push vs. pull (bisonoric)
Used in folk, Irish, Cajun, Tex‑Mex, and Alpine music.

Bayan Accordion

A refined form of the chromatic button accordion
Distinct reed construction and deeper tone
Standard in Eastern European classical repertoire.

Free‑Bass Accordion

Left hand uses single‑note bass instead of preset chords
Allows full classical polyphony
Used by advanced classical players and conservatories.

Digital / Electronic Accordion

Uses sensors instead of reeds
MIDI, onboard sounds, silent practice
Roland is the leading maker.

Concertina (Accordion Family Cousin)

Hexagonal or octagonal shape
Buttons on both ends, bisonoric or unisonoric
Includes English, Anglo, and Duet systems.

Bandoneon

Square concertina‑type instrument
Essential to Argentine tango
Complex button layout, deeply expressive tone.

Regional Variants

Steirische Harmonika (Alpine) — bisonoric, strong bass reeds
Sheng‑style accordions (Asia) — hybrid free‑reed systems
Trikitixa (Basque) — fast, bright diatonic style
Cajun accordion — single‑row diatonic with powerful reeds

Summary: The Full Definition Set

An accordion can be defined by:

Its sound mechanism: free reeds
Its air source: bellows
Its control systems: keys or buttons
Its tuning: chromatic or diatonic
Its action: unisonoric or bisonoric
Its purpose: folk, classical, jazz, regional, digital