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As much as one admires the original designers, the original intent is irrelevant to us. The designs have flown the coop and we are free to do with them whatever we can get away with. To this point, the anglo concertina was designed for what we call harmonic style: melody on the right, oompah on the left. I am sure that the designers of the Anglo concertina never foresaw, hallucinated, their use in contemporaneous Irish Traditional Music, which many of us play and admire. Bounding oneself by what one imagines their original intent was is, IMHO, silly.

I have played with (not really played) "La Poule" which seems to fits the instrument pretty well. But I don't dare yet play it in public. (Daquin's "Le coucou" also works pretty well.) And, yes, I reserve the larger concertina for playing from keyboard sheet music.

No note is too low for my concertina ?. In baroque keyboard music the lowest note I've found is the second C below middle-C. I believe that there's no lower note on the Well-tempered Clavier nor on Rameu's work, for example. Occasionally I have to play with the left hand notes that on a piano (harpsichord, clavichord) would be played with the right hand, as the lowest note on the right hand of my large concertina is the G below middle-C.

Ritonmousquetaire, (My apologies! It's me again.) I think that to answer your question one has to take into account the type of music and arrangements that one wants to play. To play baroque keyboard music directly from the standard sheet music, I would like to have an extension of four octaves plus one note: starting from the second C below middle-C and ending on the second C above middle-C. I would also like the left hand to go up to the C above middle-C and the right hand to down to the G below middle-C. That makes 67 keys in total: 37 keys on the left side plus 30 on the right hand. I know, it feels strange to have more notes on the left hand side. On the other extreme to play a melody on the right side and bass and chords on the left perhaps one can get away with four octaves or so: two octaves plus one note on the left hand side and two octaves plus one note on the right with no overlap, for a total of 50 keys. On this one, one might be able to play more complicated music by careful arrangements. Layouts in between are possible. I have a second duet concertina (also Maccann/Chidley) with 57 keys, 25 keys on the left hand side and 32 on the right. The left hand side goes to the first C below middle-c and to the first C above middle-c; the right, goes from middle-C to the third G above middle-C. Please take a look at the arrangements by David Cornell. http://www.concertina.com/cornell/ Most of the music there fits on the 57 key concertina I described below. At least on one ocassion he goes down two Gs below middle-C. However, one cannot play Bach directly from the keyboard sheet music. The larger the overlap, the less one has to think about the arrangement, I think.

Looks like a twin of mine. Does yours have riveted or hook action? (Mine has hook action.)

All the implementations I know of duet systems (Maccann, Crane, Hayden) have an overlap of typically one octave. I suppose one could eliminate the overlap. It would be the equivalent of placing a hard boundary at some point of a piano keyboard and restrict the hands to stay on their side. A nice feature of a duet with some overlap is that one can often play directly from piano scores with minor modifications; you lose this without the overlap.

A duet concertina typically provides an overlap between left and right hands. Oftentimes, the middle-C octave appears on both hands. (Sometimes the overlap is larger.) So, to cover 4 octaves plus one note, with one octave overlap, one would have 61 notes and reeds. An EC has its own overhead: each octave has 14 reeds and buttons. So, for the same span of 61 notes, one would have 57 keys and reeds. Though the difference is only four notes/reeds, as Alex pointed out, the balance is different. My brain is happier with a duet.

The left hand side spans 37 notes starting on the C two octaves below middle C. The right hand side spans 42 notes starting on the G below middle C. (I miscounted, it has 89 keys). That is, it spans 5 octaves plus one note. This is a Chidley-Maccann: differently from the standard Maccann each octave has the same layout. The Button Box had an 88- key Maccann for sale until recently. They currently have a 72-key one.

An 88-key Maccann has all the range of the standard EC on its right hand :-), so range should not be a problem. I have sat down with my 88-key Chidley-Maccann and read through some Regondi (the Hexameron, I think) and it seemed perfectly doable, but I never persevered on the project. Not a concertina but Helmut C. Jacobs plays Regondi on a CBA (I believe on a one-reed per side instrument, with single notes on the left hand): https://www.amazon.com/Giulio-Regondi-Souvenir-Compositions-Concertina/dp/B000I2IPMK/ref=sr_1_2?ie=UTF8&qid=1528116562&sr=8-2&keywords=jacobs+regondi Azurra Clementoni plays one the waltzes on the piano accordion on youtube: It seems perfectly feasible. Just make sure you have the right duet.

You are, in a way, correct; however, as a linguist, I would designate the traditional tango instrument as a Bandoneon (with a capital B ) - it's a German, bi-sonoric concertina in the so-called rheinische Tonlage (Rhineland tuning) that was developed my a Herr Band from Krefeld, hence the name. The chromatic version I would rather designate as a "bandoneon" (in quotes). It has nothing in common with the original Bandoneon except the dry-octave tuning. While many musicians can play tango music written for and with the original Bandoneon on the chromatic bandoneon, it is unlikely that music composed on the chromatic would have the character of music composed on the bisonoric original. Just my supposition, based on composing and arranging on several differnt instruments. Each instrument's limitations call for a differnt problem-solving strategy, and thus influence the music. Cheers, John Just a nit: the rheinische Tonlage bandoneon *is* chromatic (i.e., it has all notes of the scale). I would use "bi-sonoric" vs. "unisonoric" to distinguish the two types of bandoneons. We are, of course, "contándole los tres pelos al gato".

The language of Argentina and of Argentinan tango is very definetely Spanish. (Source: am native Spanish speaker.)

You are describing one particular type of bandoneon. A different type, among many types, the unisonoric, chromatic bandoneon is also in use, mostly in European countries. A description of its layout can be found here: http://atzarin.com/eng/introduction/keyboard_layouts/unisonoric_bandonions.html Olivier Manoury playing an unisonoric, chromatic bandoneon: https://www.youtube.com/watch?v=AHzzhCDgavo

Bandoneons are harder to find than concertinas or accordions. You will also find it much harder to find a teacher and/or teaching materials. Also, If you are interested in playing tango, it helps if you can read/speak Spanish. As with the concertina, there is not one type of bandoneon. The standard tango bandoneon has differrent keyboard layouts on opening and closing the bellows. Also, left and right hand layouts are not related, which means that one needs to learn four different layouts. Moreover, the layouts, IMHO, defy any logic: one has just to memorize them. There are also unisonoric chromatic bandoneons at have at their core the same layout as a C-system CBA in both hands (plus a come of extra rows). There are other types (e.g., Einheits Bandonion). Search youtube for bandoneon performances to get an idea of the range and complexity possible. If you are looking for a free reed instrument that does not limit what you can play on the left hand (exotic Jazz chords with flatted fifths and whatnot), you could take a look at free-bass accordions. Instruments, repairers, and teachers are easier to find. You might also consider the Hayden, Maccann or Chidley concertinas.

Would you have to add the width of the table saw blade kerf to the appropriate interior dimension?

Don't forget the gurdy! The closest video I've found: https://www.youtube.com/watch?v=QTiXdMkS9DY