English trad music was pushed in a different direction by davy graham who influenced martiN carthy, GRAHAM went to morooco and heard the oud and used the sound to produce a different tuning dadgad, which has led on to cgcgda dadeae, and others, .
it is of course impossible to get symapthetic ringning on a concertina, but some ideas chordal can be transferred to concertina, example using a dyad a fifth apart with the third note sharpened, using modal chords with a 7, using suspensions[of intervals of a second] but just briefly touching the discord[for maybe a half beat etc]. all of this stems or its popularisation on the uk folk scene as a result of davy graham visiting morocco.