Well, the triple row is diatonic like the single row. Each row is like a single row in a different key. If you play single row, it is very easy to pick up on some of the signature Bluesy licks. If you consider that each row basically has three major scales with some variation, the instrument is truly very versatile. Mastering THAT takes a lot of work because you have to be able to jump back and forth between mindsets. The hardest thing, for me, has been knowing where my fingers are. Some models have a thumb strap like a single row, but many do not.
If you play single row you can easily pick up the triple. Like Ganey said, look at it like it is three single rows lined up together. Same with the bass. Start out by playing all your tunes on one row at a time. You will quickly find that the box is a bit cumbersome for quick bellows changes. Then start to look for the same notes on the pull on the adjacent rows. Like Corey Ledet says on his instructional video, if you are looking for a note it is probably right there on the next row, either up or down one or two buttons. It looks daunting but it is really not. You just have to fool around with it and pick up on the relationships of the rows to different keys and chord structures. Just fool around with what you already do on the single and it will all become intuitive.
Coming first from a two row diatonic myself the journey into the 3 row and the single row has been very fun. I guess because I was half way between the two techniques. It depends how you approach the playing of the 3 row at first: push and pull or crossed button (especially on the pull). And also the style you want to play. If it is TEX-MEx you will just use the crossed button technique.
The nice thing of the 3 triple for zydeco is to try both techniques: push and pull and crossed button techniques. If you watch the masters of the genre (zydeco) you will see the variety of choices depending on the type of approach they have chosen.
The fun part for me has been adapting the techniques of the 1 row (or even 2 row) to the triple row which will lead you to a lot of push and pull. At the beginning it seems hard and impossible because of the weight of the accordion but it comes easy as you keep practising. Doing that you get really close to most of the Caribbean and latin American techniques of the triple row (2 row) and shows you the similarities with cajun, zydeco and creole music.
At the beginning- because of the amount of buttons- you get lost and you think you have to cross buttons all the time. Don't get overwhelmed, approach it as a diatonic instrument at first (as most of the old players have done) and bit by bit recognise the chromatic possibilities of the instrument. For me the easiest has been going gradually from the push and pull into minimising the effort on the bellows by finding the same note on the row beside. It takes a while until you understand the possibilities (of techniques,notes and styles) of the instrument. But it gets there.
Switching from accordion constantly helps to the development. Especially for speed and losing fingers. At least for me.
My humble two cents (I hope i didn't confused you)
Good luck
On link#2 you can look at several keyboard layouts from all kind of melodeons. Most of the instruments have a diatonic scale on each row. I hope that's the right way to mention it. The Irish two row are chromatic ones(?), because they have rows like C#/D or B/C and there are also three rows which you can use as a chromatic one like B/C/C#. I think that playing this instruments is also different than playing a three row with A/D/G.
I stay with the one row, because increasing of the amount of buttons also makes it more difficult
Though the "Irish" 2 row 1/2 step boxes are chromatic and in theory you can play in all keys... they are played usually in D, G, A and their relative minors. Other 1/2 step systems are the D/D# and the C/C#.
The B/C/C# system was favored by the Scottish player Jimmy Shand. There was a very expensive Hohner Jimmy Shand model... highly prized.
The B/C/C# boxes have a Stradella (piano accordeon) style bass system.
Another hybrid is the C#/D/G to allow playing in the English D/G system and also the Irish C#/D system.
Variants are the C#/D/D#
Another older widely used system was the G/C/B system used by the French.
Often these had Stradella bass systems and were known as "mixte" accordeons.
I wouldn't consider an Irish B/C or B/C/C# as chromatic. I think they're still diatonic, though you can get the total chromatic scale by going across rows.
I think chromatic TENDS to mean that it has all the notes of the chromatic scale when pushing in the same direction, and that notes on the pull are the same note as on the push.
I also think this is somewhat of a grey area, but leans heaving to what I just recounted.
A piano accordion is chromatic. A 3 or 5 row chromatic is chromatic.
This all is very interesting and i didn't know anything about all those different systems. Am I right if I say that each row on a Irish have a diatonic scale, but together with the other row you have chromatic possibiities?
CBA or Chromatic Button accordeons are also known as Continental Chromatics.
They come in "B" systems or "C" systems. also known as B Griff or C Griff.
They are usually 4 row or 5 row.. I have seen 6 rows but these were the Russian versions known as BAYAN.
These are not diatonic.
If I were starting accordeon all over..I would start,and stay with a CBA.