"John O'Reilly", in Gaelic "Sean Ua Ragallaig" is an Irish air or planxty in 6/8 time). The tune is in two parts: the A part is in A Major and the B part is in A Mixolydian. The parts are played as ABA, AAB or AABB. It was supposedly composed by blind Irish harper Turlough O'Carolan (1670-1738), according to Chicago flute player and collector Francis O'Neill, apparently relying on the assertion of Hardiman, who maintained that it had been composed by the bard for members of 'the great Cavan family' of O'Reilly. O'Sullivan (1958) included the air in his seminal work on O'Carolan, but concluded that there was no significant evidence that it had been composed by the harper. Collector Edward Bunting (1773-1843), who is the sole printed source, collected the tune from ancient harper Arthur O'Neill, but does not attribute the melody to anyone. Thomas Moore used the melody for his song "Oh! Think not my spirits are always as light" published in Irish Melodies, vol. 1 (1808). It was printed in Bunting's General Collection of Ancient Music of Ireland (1796), Clinton's Gems of Ireland (1841), Complete Collection of Carolan's Irish Tunes (1984), P.M. Haverty's One Hundred Irish Airs vol. 2 (1858), Levey's Dance Music of Ireland, 2nd Collection (1873), O'Flannagan's The Hibernia Collection (1860), O'Neill's Music of Ireland: 1850 Melodies (1903) and O'Sullivan's Carolan: The Life, Times and Music of an Irish Harper (1958).