Guide

Accordion bass buttons: the melodeon left hand, and Stradella

By SGWNI, 25 October 2026

The buttons under your left hand are the bass side. On most melodeons, almost every one of them plays a different note on the push and the pull. On a piano accordion or chromatic button accordion, with the Stradella system, each button always plays the same thing. That one difference explains most of what the left hand does.

Which system have you got?

Hold a bass button down and change the bellows direction, then try two or three others. If the sound changes, you have a diatonic bass, the kind on a melodeon. One pair on most melodeons is the same both ways (C on a D/G, F on a G/C), so don't judge by one button. If none of them change, it's probably Stradella.

Counting the buttons won't settle it. A two-row melodeon usually has eight basses, but small Stradella boards also come with eight or twelve. Signs of Stradella are rows of buttons that run in fifths and a C button marked with a dimple or stud in the second row from the bellows.

Chords and basses on a melodeon

A two-row melodeon usually has eight bass buttons in two rows of four, and they come in pairs: one plays a chord, its neighbour a single bass note with the same name. You'll often play the bass note on the strong beats and the chord in between, which is the oom-pah, or chords alone on the off-beats.

In the tables below, the outer row is the one further from the bellows, with the home chords of the two treble rows. The inner row is the one next to the bellows.

The D/G bass

Row	Pair	Push	Pull
Outer	First	D	A
	Second	G	D
Inner	First	B	Em
	Second	C	C

Each line is a chord button and its bass button, which share a name. On the outer row the push gives you D and G, the home chords of the two treble rows. The pull gives A and D, the chords that lead back to them, so D is there in both directions. The inner row adds B major with E minor, and C on both push and pull. Some players have B minor in place of B major.

The G/C bass

Row	Pair	Push	Pull
Outer	First	G	D
	Second	C	G
Inner	First	E	Am
	Second	F	F

The same pattern a fifth lower: G and C on the push, D and G on the pull, then E major with A minor, and F both ways.

Why the left hand follows the bellows

Both hands share one pair of bellows. If the bar wants a G chord on a standard eight-bass D/G, you have to be pushing, because that's the only place G is. If the melody in that bar is being played on the pull, the G chord simply isn't there.

So the left hand often decides the right. A player will choose a push note on the other row to keep the bellows going the way the chord needs, or let the chord go and play a bass note that works on the pull. That's a large part of why fingering on a melodeon is a matter of choice, and why the same tune can be tabbed several ways.

The C on a D/G, and the F on a G/C, are the exceptions: the same both ways, so they fit wherever the bellows happen to be going.

Other diatonic bass layouts

One-row boxes have two basses: on a one-row D, a chord and a bass that give D on the push and A on the pull. Some have four.
Twelve-bass two-rows add a chord and bass pair at the chin end of each row, and makers choose different ones. Castagnari adds E♭ major with F♯ minor, and B♭ with F. Saltarelle adds A with G, and F♯ minor with F, which puts a G chord on the pull.
B/C and C♯/D boxes, the Irish button accordions, have eight basses. The outer row of a B/C is the same as a G/C's; the inner row differs, with A major rather than A minor on the pull and C push, F pull on the last pair. There's no pair that's the same both ways. The B/C chart has the details and the variations.
The Basque trikitixa is the odd one out: its twelve basses are the same on push and pull.

The Stradella system

Piano accordions and chromatic button accordions nearly all use Stradella. Its buttons sit in rows parallel to the bellows. On a full board there are six, counting from the bellows outwards: counter-bass notes, bass notes, then major, minor, seventh and diminished chords.

Each line across the rows belongs to one key: for C, that's E as the counter-bass, C as the bass, then C major, C minor, C7 and C diminished. Moving along a row, each button is a fifth above the last, so the three main chords of any key sit side by side.

The chords are fixed by the reeds. The seventh button leaves out the fifth, so C7 sounds C, E and B♭, and the diminished button is a diminished seventh without its fifth. Each bass reed set has only twelve reeds, one octave, so a bass button plays a note name rather than one fixed pitch, and a scale on the basses drops back an octave part way up.

Common sizes

Basses	Rows of buttons	What's there
8 or 12	2	bass notes and major chords
24	3	adds minor chords
48	4	adds counter-bass notes
72, 96 or 120	6	adds seventh and diminished chords

Those are the usual layouts, not a rule: some 48-bass boards have six short rows instead of four long ones. Free-bass accordions go further and give the left hand single notes over three octaves or more, usually with a switch that converts some rows from Stradella.

The air button and the strap

Both kinds of box have an air button, under the left thumb, which lets air in or out without sounding a note. It matters more on a melodeon, where the chord you want can depend on the bellows direction. The left hand goes through the bass strap, pushed in far enough for the little finger to reach the furthest button.