Ok, I was going to stay out of this but....

As I understand it the individuals concerned were asked by the festival organisers to come along and play tunes in the session area - both to attract a crowd and keep the session momentum going. That's what they did. End of.

Speaking from personal experience of playing with these guys (and girls) they're a bunch of top class musicians equally happy playing trad, contemporary or self penned tunes (hence being asked to play at festivals by festival organisers). Some sets of tunes (mainly trad) have become well practised by these guys over the years (of meeting up at sessiona) so I can see how it may sound like a performance set on occasion. But really it's all about having fun with the music and that means joining in with anybody and everybodys tunes. I guess that's why 'Ruth Archer' felt so welcomed - because she got the atttude right....

/2p

The other accordion player (HRH Wales).