French became renowned for composing and singing comic songs and gained considerable distinction with such songs as Phil the Fluther's Ball, Slattery's Mounted Foot, and The Mountains of Mourne (this last was one of several written with his friend, stage partner and fellow composer, Houston Collisson).
One of French's most famous songs is "Are Ye Right There Michael", a song ridiculing the state of the rail system in rural County Clare. The song caused such embarrassment to the rail company that it led to a libel action against French, though this ultimately failed. It is said that French arrived late for the libel hearing at the court, and when questioned by the judge on his lateness, he responded "Your honour, I travelled by the West Clare Railway", resulting in the case being thrown out.
French became ill while performing in Glasgow and died some days later (from pneumonia) in Formby at the home of his cousin, Canon Richardson of Green Lea, College Avenue, on 24 January 1920, aged 65. His grave is in the churchyard of St. Luke's Parish Church, Formby, Merseyside. A statue of him sitting on a park bench in the town center of Ballyjamesduff in honour of him and his famous song, "Come Back Paddy Reilly to Ballyjamesduff".