Aurican is the harpist in question. In all honesty he doubted about using this particular song, but as the ceremony proceed he starts to understand why this song is used.

Of course, he doesn't know that this isn't any ordinary wedding ceremony because, well, this is his first time being in one. Dragons don't marry, after all.

So he continues with his performance and hopes everyone will enjoy it just as much as the exchanging of vows.