Catchy composition of Niall Vallely.
The first phrase is like that of one of his earlier tunes:
Should be Fm
Prefer it in Am myself
Great rendition for this tune here!
I think it’s in DMajor as i post on the transcription above: (The tune starts at 7m28s)
A tin whistle version here
On the Buille 2 CD, the tune is in F minor, or some F modal key. That is, a half tone higher than the first version of sheet music with a G sharp in the key signature. Or a half tone lower than the one with 3 sharps, labeled A maj. But I don’t mind playing it in either of those, which are easier than the way it is recorded.