Taking as its subject the small Gaelic-speaking community of Tory Island off the Donegal coast of Ireland, On a Rock in the Middle of the Ocean tries to answer the deceptively simple question of why people sing. The book focuses on aspects of song transmission and performance, showing how early exposure to musical culture led certain individuals to be singled out and given special encouragement to express themselves. Individual desire and ability to overcome the rigors of social scrutiny are important factors in the development of an active public performer.

In a special study of one song, author Lillis Ó Laoire shows how the song itself emerges as a mediator of dilemmas and tensions in island life. In a meticulous exposition of the links between music, text, and performance, the vicissitudes of island life are revealed while these tensions are alleviated by singing humorous ribald lyrics to provide a deliberate contrast.

Comparisons are drawn to argue that the interpretation of songs to reveal particular worlds of meaning is a widespread human activity, found in similar configurations at both global and local levels. In Tory's context, the book further asserts that such mediation contributes to a strongly realized sense of identity and historical continuity among the islanders. The book includes an audio CD of folk music from Tory Island, featuring traditional ballads, tunes, and dances.