As a child at primary school in the early '50s -- with no Welsh background at all -- I was VERY taken by a song from our music book of 'Folk, National and Art Songs of the British Isles' (or something similar).

The title was 'David of the White Rock' (from the Welsh section of the book) and the nature of the tune suggested to me, even at that age, that it was possibly an air rather than originally a song.

But I have no idea where you might find musical notation….

(Hope all goes well with finding something suitable and accessible.)