The book represents an exploration of three Irish-language mass settings for the Roman Rite, two by Seán and one by Peadar Ó Riada, written from within the cultural context of the Gaeltacht of Cúil Aodha. In it the author highlights the significance of the achievements of both composers (particularly the younger of the two), validating their work against the heritage, discipline and compositional principles of western plainchant and heralding its significance as a model for contemporary vernacular liturgical music.It should be of interest to theologians, liturgists, liturgical musicians, musicologists, chant scholars and indeed ethnomusicologists. The Ó Riada aspect will its own market, particularly in Ireland. It presents an investigation into the liturgical music of Seán and Peadar Ó Riada through an examination of three Roman-Rite mass settings composed in the Irish vernacular from within the cultural context of the West-Cork Gaeltacht of Múscraí. The main part of the work, running from Chapters Three to Six, consists of a detailed analysis of the contents of the mass settings, a body of material which is considered from the following perspectives: as emanating from a living culture of native traditional song; as part of a historical continuum of monophonic liturgical composition for the Roman Rite, having at its origins the compositional traditions of plainchant; as part of a broader aesthetic context of text-music relationships found in the repertoires of plainchant, medieval song and folksong; and finally, as part of the new liturgical reality existing since the Second Vatican Council which requires viable and sustainable musical approaches to the setting of vernacular texts.