If you are an accordion player you will already familiar with playing chords on the bass side of your instrument. But it can also be included in concertina-playing. In some styles this is standard, e.g  playing traditional English or Aussie waltzes, schottisches, marches.

But it can also be included in playing Irish dance music, though more minimally. Micheal O”Raghallaigh is perhaps the best exponent of this. . This invariably done with the lower keys on the LHS. Unlike an accordion, where one button will play a triad or 5th chord, the concertina requires you to play the individual notes of the chord. But generally a full triad ( 3 buttons) is unnecessary or too awkward.  And of course you may stay on the chord for only a quaver or 2, because as soon as there’s a bellows change the chord is lost. But such brief chordal pulses are enough to really enrich the sound. You don’t want to overwhelm the melody with a loud, over-long chord. Very often all you need is a drone, one bass note to add extra timbre and depth to a phrase or crucial note, or maybe by adding the 5th of the triad chord, or less often the 3rd .

The main combinations  I use are –

G major –  G, and D on the press, using the flattened left pinky across both buttons. Some times I also add the G at G3.

D major I use a 5th chord here, on the draw – D at C3, with either of the drawn A’s on the LHS. I generally don’t bother with inserting the F#.

C major – I use the pressed C at C3, of course, sometimes combining it with the E, and/or either of the pressed G’s. Sometimes for extra effect, say if it’s at the end of a phrase, I use the very bottom C, provided my pinky can get down there fast enough.

E minor –  with the E I include the adjacent pressed G at C5. but I find bringing in the pressed B makes this chord more dramatic. In theory one should be able to flatten the middle left finger across these 2 buttons ( C4 and G4), as with the G chord above, but my straps are too tight to do that

You may also choose to use the pressed bass E, at T1which combines beautifully with the B. Generally, as with most chords, you’re playing these when there’s a melody note on the RHS, i.e. here, the pressed e, g or b.

 A minor – you could play the drawn A at G3 with either or both of  the  c or e on the next 2 buttons, but I like to bring in the drawn bass A, at G1  too. Adding the A and the e to it make a very powerful chord.

B minor – I use 2 different combinations here: the drawn low B,  with F# ( don’t bother including the drawn D), which gives a rich deep 5th chord ( Micheal O’Raghallaigh uses this gorgeously  to open  the jig Hawthorne Hedge on his Nervous Man CD). Otherwise you use the F# with the drawn B at C5, and/or the d at C6.

D minor – as for the D major, play a 5th chord with either of the 2 A’s.

This is a very individual  matter. Work out the most tasteful and technically feasible combinations as you go. Here’s an example: a score for a polka with all the chords included  – Ballydesmond Polka ( one of many Ballydesmonds)

Lastly,  to give you the theory to build the chords, here are THE BASIC CHORD TRIADS. 

Here are some diagrams of the chord fingerings.