Synge's musical ability made a strong impression on Handel when the composer was in Dublin; Handel referred to Synge as 'a Nobleman very learned in Musick'. Synge was in attendance at the first performance of Handel's Messiah and his written comments on the performance are quoted in Richard Luckett's Handel's Messiah: a celebration (1992).
Synge is particularly well known for his 221 letters to his daughter Alicia (1733-1807) the only survivor out of the six children of the Bishop and his wife Jane Curtis (d. 1737) whom he married in 1720. These are principally taken up with advice to Alicia whom Mary Delany said was being 'brought up like a princess' . There is almost no aspect of the young girl's life upon which her father did not comment including dress, health, diet, exercise and behaviour in social situations. His principal concern was with her education generally and specifically her ability to write letters well; his advice to her on this score was to copy Swift for grammar and punctuation. These letters also provide valuable insight into domestic life and the lives of servants. The bequest of these letters to the Library of Trinity College, the University of Dublin, by Synge's descendant Marie-Louise Jenner, has revolutionised eighteenth-century Irish social and women's history.
Synge died in office on 27 January 1762, aged 71.