It's not useful to obsess about 'authenticity' of the music. I very much doubt anyone going for an "auld Oitish tune, from Ireland' would come up with Gary open, that one is a dolly American obsession after Custer and all that. 'I dreamt that I dwelt in marble halls' you asked after in another post is from the 1843 opera 'the Bohemian girl' by Balfe.That doesn't fit the timeliness very well. But does it matter?