I think the audio is done in a studio and then some very slick editing is done to sync it up.Its 2 different videos if you notice in one shot Hayden has a cigarette behind his ear but in the other shot he doesn't.

This one of Matt Heckler playing his violin sitting on the cliffs of Moher in Ireland must be studio audio synced up,the wind and sound of the waves crashing would certainly be heard while recording out in the field.

Slick editing, very slick :)