Here is a wonderful 1976 recording of Paul Brady, supported by ‘Planxty’ members Andy Irvine and Donal Lunny, singing ‘Mary and the Soldier’. Paul was much more of a traditional singer in those days than he is today. The lyrics can be found here.
The Cantaria Folk Song Archive has this to say about this song:
This is one of the countless “trooper and the maid” songs, but with a happy ending. In some the girl dresses up as a boy to follow her soldier, enlist, etc. In most cases she’s left heart-broken or worse. This particular song is also known as The Gallant Soldier, and in the Scottish tradition as The Hieland Sodger or The Highland Soldier. See also The Trooper and the Maid
Mary learned this song from the singing of Paul Brady on the album Andy Irvine and Paul Brady (available from the Chivalry Music store).
This version was collected by Sam Henry from Dick Galloway in 1938, who learned it in Magilligan. In Sam Henry’s Songs of the People, he quotes the source: “… Magilligan, a land full of melody, traceable in part to the influence of its great harper — Dennis Hempson (born 1695, died 1812).”
Paul Brady is one of the best known Irish folk/pop singer-songwriters today; his website is here. His songs have been covered by Bonnie Raitt, Tina Turner, and Santana, among others.
Andy Irvine and Donal Lunny were members of the iconic Irish folk band Planxty, with which Paul Brady was also briefly associated.