I believe Billy McComiskey told me that the late great Paddy O'Brien (As opposed to one great box player of the same name who is still very much alive) played a large role in the current dominance of the B/C ...
In Ireland he is commonly referred to as "Paddy O'Brien from Nenagh", to differentiate between the two, and it may be no exaggeration to say that probably one of the most important events in Irish accordion history was his fifteenth birthday, on 10th February 1937, for which he was given a B/C accordion that he had asked for (one account has it that the instrument was one of the new Hohner Black Dots, whilst another says it was a Paolo Soprani). He had started to play the fiddle at the age of seven, and three years later took up the G/G# accordion, which he played with the Lough Derg Ceili Band, and for a 1936 radio broadcast with his father Dinny O'Brien on fiddle (though he too played the accordion), and Bill Fahy on flute.
Paddy O'Brien wasn't the first to play the B/C (and Sonny Brogan made earlier recordings on the instrument), but he perfected the B/C style and the handful of 78rpm recordings he made in 1953, before emigrating to New York in January 1954, were to inspire many to take up a whole new, "modern" style of playing that had more to do with fiddle style and ornamentation than that of the melodeon. Reg Hall has commented on how, in the late 1950's, all the young Irish accordion players in London pubs were playing "The Yellow Tinker" and "The Sally Gardens", as learned from Paddy O'Brien's most famous record.
However, from my own experiences of some of those same players, a decade-and-a-half later, I can add that many of those 1950's "young bucks" of the Irish accordion seem to have also been influenced by the recordings of Jimmy Shand around the same time, and were just as likely to know his chart hit "The Blubell Polka." Indeed some even took up, or experimented with, the B/C/C# "Shand Morino", though it would be very rare to see a 3-row in Irish circles today.
... and that other players like Joe Burke have kept it popular.
Joe Burke was born in Kilnadeema, Co. Galway in 1939, and both his mother Annie, as well as his uncle Pat, played the accordion. About the age of four, he too started off on a Hohner G/G#, on which his uncle showed him a couple of tunes, and I memorably heard him say that "at that time we thought the second row was in case anything went wrong with the other one; a spare" and "I was even told that one row was for jigs and the other one was for reels !"
That was until a man called Martin Grace, an accomplished accordion player who had an unusual style for the time (playing across the two rows), visited the farm with a threshing machine, and was sitting in the kitchen drinking tea when he saw the accordion under the table. He asked who played and proceeded to knock out a few tunes. Joe had never heard this style of playing before and Martin showed him some of the basic rudiments of his accordion technique. Martin Grace was involved with the renowned Ballinakill Céilí Band with Aggie Whyte in the forties, and he played with that band for many years.
Joe Burke and his first B/C, Gort Feis 1955.
It seems that Joe also got his first B/C around the age of 15 (c.1954), progressing on it at such an amazing rate that he won the Senior All Ireland button accordion competitions both at the 1959 Fleadh Cheoil in Thurles, and 1960 in Boyle, before withdrawing from competition. He acknowledges being inspired by the B/C playing of both Paddy O'Brien ("Those 78's had a huge impact on me, especially The Spike Island Lassies/Dowd's Favourite, it was a revelation") and Kevin Keegan (from Ballinasloe, Co. Galway), as well as the C#/D and D/D# player Joe Cooley (from Peterswell, Co. Galway), "because they were the first accordionists I ever heard play like fiddlers" - but the biggest inspiration for subsequent generations has been himself...
Paddy O'Brien and Joe Cooley.
On the flip side players like Jackie Daley are definitely responsible for making the C#/D popular again.
That is a complex issue, as I said recently :
Ironically, the C#/D style of playing is the older one, but accordions in that tuning seem not to have become available until the mid 1950's, so that prior to that it was played on instruments in D/D#, C/C# or B/C and the fiddlers had to tune up, or down, to suit (indeed, I know of situations where they still have to !).
The old style never went away, but "concert pitch"* instruments in C#/D were actually quite rare, so its players were usually playing in the "wrong" key. This no doubt helped to discredit the old style, especially with the rise of the new "concert pitch" B/C, but certainly Jackie Daly has been a major influence in promoting C#/D and getting younger players to take up the old style. There are now more C#/D accordions in circulation than ever before, though the B/C is still very much the dominant system in Ireland.
Paolo Soprani C#/D, made in late 1954 and one of the first in that tuning.
* In Irish traditional music terms, "concert pitch" = playing in D.
Edited to add paragraph about Martin Grace.
Edited by Stephen Chambers, 24 March 2017 - 02:05 AM.