Complex sentence: It was set to the traditional air "The Dawning of the Day" ("Fáinne Geal an Lae") composed by Thomas Connellan in the 17th Century.
Split into simpler sentences: It was set to the music of the traditional song "The Dawning of the Day" ("Fáinne Geal an Lae "). An air called"Fáinne Geal an Lae" was composed by Thomas Connellan in the 17th Century.