Compositions by Arvo Pärt have been frequently described as alluding to medieval compositional practices and sound. Miserere (1989, revised 1992)—a work for soloists, chorus, and instrumental ensemble that sets Psalm 50/51 and the thirteenth-century Dies irae hymn—makes a useful case study of his engagement with medievalism, particularly its aesthetic, theological, and reception-based dimensions. Over a period of three decades, Miserere has been subject to numerous interpretations and has been absorbed into the labor of culture and commerce. This study considers three aspects of its story: first, how Pärt’s tintinnabuli technique, which emphasizes creative rebirth through early music, relates to the composition of Miserere; second, how the relationship of his music to the medieval has been immortalized in recording and debated by the academy; and finally, how his music has been popularly received and drawn into other media, including its evocations of virtual liturgy. This complex crossroad—what I later term “third-space medievalism”—can be characterized as a tension between the ontologies of tintinnabuli and its claims regarding the authority of early music; the alignment of Pärt’s music with medieval music praxis; the commercial immortalization of Pärt as both belonging to a premodern past and anticipating the postmodern future; the labor of some commentators to reconcile Pärt between modernism and postmodernism; the utility of Pärt’s music in the evocation of asynchrony in the moving image; and finally the positioning of Pärt’s music as a text encoded with images from a pre-Enlightenment world.