- The difference comes down to one word: bisonority. A diatonic accordion button gives two notes, one when pushing, one when pulling
- The chromatic is unisonorous: one key, one note, in both directions of the bellows
- The diatonic is tuned in one or two keys (G/C, A/D). The chromatic has them all
- The common points remain the majority: bellows, free reeds, melody on the right, basses and chords on the left
There is a mistake that often comes back, and it costs the price of a method book: buying a fingering collection that doesn’t fit because it is written for the other accordion family. A diatonic accordion method won’t open on a chromatic, and vice versa. Yet the two instruments share almost everything: same bellows, same reeds, same way of carrying on the straps. The difference lies in an internal mechanism that no one sees, and that changes everything from the first sustained note. Here is what really separates the two families, what they share, and how to know which one matches the music you want to play.
Diatonic or chromatic accordion: the difference
On a diatonic accordion, the same button gives two different notes depending on whether you push or pull the bellows, and the instrument is tuned in one or two specific keys. On a chromatic accordion, a key always gives the same note in both directions, and all twelve semitones are present, so all keys. The rest, keyboard, number of basses, weight, repertoire, follows from these two points.
The test takes three seconds. Hold a button down, push the bellows, then pull without releasing the finger. If the pitch changes, it’s a diatonic. If it stays the same, it’s a chromatic. On an ad, compare the number of buttons and the number of notes: 21 buttons for 42 notes, the count is doubled, it’s a diatonic.
The similarities: bellows, free reeds and two-hand logic
Before looking at what separates them, you have to see what unites them: that’s the biggest part of the topic. Diatonic and chromatic are two free reed instruments, where a metal tongue vibrates in its frame when the bellows air passes through it. Neither sounds without bellows movement: the arm gesture is the accordionist’s bow, and it carries the dynamics.
The playing setup is common too: right hand the melody, left hand basses and pre-made chords that fall under the fingers. Same way of carrying, same maintenance, same tuning entrusted to a specialized tuner. Accordion accessories also work from one family to the other, straps and belts included.
The diatonic accordion: bisonorous and tuned in keys
A diatonic accordion does not give the twelve semitones of the scale. It is built in one or two keys, usually indicated in the model name: G/C, A/D, C/F, D/G. Each row of buttons corresponds to a key, and a piece in a distant key requires borrowed fingerings. That’s the instrument’s logic: the repertoire of dance halls, dance and traditional song lives in these keys.
The left hand follows the same economy of means: eight basses on a two-row, twelve or forty on larger formats. They also work in bisonory, which sets up the dance hall pump almost by itself, bass on push and chord on pull.
The Hohner 2915 Gold Brand sums up the diatonic logic in two numbers: 21 buttons on the right hand on 2 rows, for 42 notes. The double count marks the bisonority. The left hand holds 8 traditional basses in 2 voices. Tuned in G/C, it also exists in A/D, C/F and D/G. Hohner highlights its acoustic power: 2 voices on the right that stand out above an ensemble without amplification.
Pros
- 21 buttons for 42 notes: one note on push, another on pull
- 8 traditional basses in 2 voices, the dance hall pump under the fingers
- Four tunings in the catalog: G/C, A/D, C/F and D/G
- 2.6 kg for 28 cm x 15 cm, wooden body and leather straps
Cons
- Keys distant from the tuning require borrowed fingerings
- Compact accompaniment on 8 basses, no register
The accordion patented by Cyrill Demian in Vienna in 1829 was diatonic and bisonorous: the original system is that of the diatonic. The chromatic button keyboard arrived about twenty years later, the piano keyboard soon after. Same root, two paths.
The chromatic accordion: unisonorous and complete
A chromatic gives the twelve semitones, in all keys, without changing instrument. Watch out for the vocabulary trap, the most common of all: “chromatic” refers to a system, not a keyboard form. It exists in two formats, the piano keyboard with its white and black keys, and the button keyboard, more compact at equal range. Both play exactly the same notes.
On the left hand, the chromatic switches to standard basses, also called Stradella basses: 48, 72, 96 or 120 depending on the model, on six rows. Two rows of basses, then rows of major, minor, dominant seventh and diminished seventh chords. Enough to harmonize an entire song without leaving hand position.
The Hohner Bravo III 72 is a piano keyboard chromatic accordion: 34 keys for the right hand for 34 notes, one key one note, in both directions of the bellows. The left hand has 72 basses on 6 rows, the standard layout on which accompaniment automatisms are built, with a range from G to E. On the timbre side, 3 voices on the right and 4 on the left, 5 registers on the right and 2 on the left. It weighs 7.4 kg and comes with a case and straps.
Pros
- 34 piano keys for 34 notes: the same pitch on push and pull
- 72 basses on 6 rows, enough to harmonize an entire piece
- The twelve semitones: all keys on the same instrument
- 5 registers on the right and 2 on the left, case and straps included
Cons
- The full keyboard requires some learning time before the first pieces
- 7.4 kg, a size to consider for standing play
Summary of the differences
The two instruments above, representatives of their family, compared line by line.
Diatonic or chromatic accordion: which to choose
It’s the repertoire that decides, not the level or the budget: both families have their virtuosos and beginners. One very concrete criterion adds itself, the circle you play with. If the people you play with are all in G/C, showing up with an A/D complicates sessions.
- Folk dance, Breton trad, Irish, Cajun, Tex-Mex, sea shanties: the diatonic is the instrument of these musics, and the bellows gesture is part of the style
- Musette, chanson, pop, jazz, classical: the chromatic follows the repertoire everywhere, because it modulates and changes key without constraint
- You play by ear, standing, in sessions: the diatonic, light and immediate, suits this practice
- You come from piano and read music: the piano keyboard gives you your landmarks from the first minute
- You aim for conservatory: accordion classes work on chromatic, most often button type
Try both the same day, one after the other, on the same simple piece: thirty minutes is enough to feel which one speaks to you. And whatever your choice, plan for the case right from the start, the bellows don’t like shocks and humidity much. They are chosen by the number of basses.
The most common confusions
- “Button keyboard, so diatonic”: no. The button keyboard is also the most common chromatic format in conservatories. Look at the rows, not the shape of the keys
- “Piano keyboard, so easier”: visual landmarks are immediate, but the left hand is learned from scratch on both sides
- A method only applies to one system: fingerings have nothing to do with each family, check the mention before ordering a accordion method
Bisonoric versus unisonoric, chosen keys versus full scale: that’s what really separates the two families. The surest way to decide remains to push and pull on both, one after the other, and see which one makes you want to keep going.
