In his notes to the song "Caitilín Ní Uallacháin" as published in Songs of the Irish, compiler Donal O'Sullivan writes that although the tune most associated with the song is one that Edward Bunting collected from the harper Charles Byrne in 1806 and subsequently published under the title "Kitty Nowlan"; he has chosen to set the words to a more suitable-sounding tune from Bunting's manuscripts, a tune with the similar title of "Kathleen Nowlan". Of this latter tune O'Sullivan writes, "A verson, called 'The Tailor's Son', was noted from oral tradition by Lady Ferguson, and the well-known song 'The Lark in the Clear Air' was written to it by her husband Sir Samuel Ferguson, the poet."

This tune "Caitilín Ní Uallacháin / Kathleen Nowlan" is indeed very similar to that of the Lark in the Clear Air. If you have a tune with a similar name and it doesn't sound like the Lark ..., it is probably the other Kitty Nowlan//Cáit Ní Nualain/Ní Uallacháin collected from Charles Byrne of Co. Leitrim.