Malcolm Douglas,I think the shift in playing styles is partly due to Comhaltas.,[Who came into existence1951]they have a system of marking which gives a relatively high proportion of marks for ornamentation.
Competitors erroneously think,the more ornamentation the better.
That is why I find Edel Fox,s comments about too much ornamentation in reels so refreshing.,however there is in my experience an inconsistency among judges over this sort of thing.
If one listens too Mrs Crotty[a 1940/1950 player] there is less ornamentation than Noel Hill or Edel Fox,this could be partly to do with music evolving or partly due to Comhaltas[Idont know if Noel Hill was a comhaltas competitor or not]
MrsCrooty and Kitty Hayes,played/play quite a lot inCmajor and D dorian[Minor]while male players like Chris Droney,play in Gmajor AND Dmajor ,EDorian,this could be because at the time1940to1980 ,women in Ireland did not go out to pubs,Men did and therefore played in the keys that were easier to accomodate the fiddle Gmajor AND d Major.