This thesis takes the form of an exploration and discourse on koinonia (a New Testament concept meaning `communion' used by St Paul in his discussions of the nature of the church) and its potential application to the shaping of a better understanding of music for worship and its use in liturgical worship. It falls into three parts. While the investigation is relevant and applicable to the Western Church in general, the thesis relates specifically to the locale, culture and religious traditions of Scotland. Part One (chapters 2-5) begins with a consideration of recent debate on liturgy and music, taking as its starting point the outcomes of the 1997 congress of Societas Liturgica on that theme. This is followed (chapter 3) by a review of recent theological writings about music and music in worship, and (chapter 4) a consideration of five dimensions of koinonia derived in particular from reports of recent ecumenical dialogue and a related ecclesiological model (following on from Gordon Lathrop) as the basis for an alternative mode for discourse on music in worship with greater potential for application and implementation in the local church. This part ends with a summary overview of selected branches of musicology as resources to enhance theological discussion of liturgical music. Part Two consists of just one long chapter (chapter 6). Here the findings from wider theological discourse on music and the insights gained from aspects of musicology are used to inform the investigation of each of the five dimensions of koinonia as the basis for the evaluation of liturgical music within an ecclesiological model: eucharistic community, relational community, community growing into maturity in Christ, diaconal community, diverse community. Part Three is more applied. Three contrasting case studies are explored (chapter 7) for signs of koinonia that might illuminate the preparation of a usable resource derived from the findings of Part Two. Each is directly related to the writer's own experience: the preparation of the third and fourth editions of the Scottish-produced Church Hymnary; the Wild Goose Worship Group of the Iona Community; the Craigmillar Festival. As evidence of current practice and attitudes, two enquiries into local churches are reported (chapter 8). The final chapter offers an outline for a discourse based on the findings of the thesis so far in a form that might be used in a local church. Taking each of the five dimensions of koinonia, this addresses both the strengthening of that church and its individual members through the discussion of music, and the better understanding of the evaluation and use of music in worship through the exploration of faith and the nature of church.