Vic, "but the changes that his playing on a C/G anglo-concertina brought by his interpretation."quote
That is your subjective opinion about his playing.,it is not a fact.
I recorded-"yesterday" and played it on a concertina ,it does not make it a folk tune, it might be a beautiful tune, That is neither here nor there, it is still a composition by Sir James Paul McCartney
Edelweiss is a composition by Richard Rodgers, That is a fact.
in theory, anyone getting paid for playing it should pay royalties, the fact that folk musicians might occasionally play composed poptunes does not suddenly make the composition a folk tune