Seventeenth-century monarchy was performed, by ritual, by enactments, by sounds, and by visualizations. The crises of European monarchies of the 1620s and 1630s were met with splendid spectacles in which rulers and courtiers acted out idealized royal virtues and power. This article argues the case for the vital importance of music within these spectacles. Musical harmony was thought to mirror the harmony of the spheres, indicating God's plan for the universe. The ruler's ability to master or evoke musical harmony in aulic theatre could thus function as double representation of divine approval of his or her government. By comparing ballets and masques at the French Court of Louis XIII and the British Court of Charles I, music's centrality to political power in the performance of sacral kingship will be demonstrated. A focus on Britannia Triumphans (1638) and Merlaison (1635), works known for the extraordinary attention Charles I and respectively Louis XIII devoted to their performances, exemplifies how the handling of music offers valuable insights into the inner power structures of those courts. In both cases the musical performance was used to communicate and establish related political agendas.