Harmony’s semantic links across music and the social domain mean that when evoked in the context of music in peacebuilding, harmony provides both a description of musical action, and an aspirational projection of the desired social outcome. However, in both domains, harmony’s foundational values and implied practices raise questions of how apt it is as a representation, tool, or goal of contemporary peacebuilding. This article seeks to answer these questions. Conceptual in scope, it examines the multiple concepts attached to harmony in the musical and sociocultural domains, and discusses these in relation to peacebuilding, illustrating some of the possible alignments and alliances with examples of cross-community music projects. It offers a heuristic for considering harmony and its values, practices, affordances, and implications from a more critical and nuanced perspective.