The organ constituted a prominent and lavishly supported voice for the church from at least the late fourteenth century. In tracing the various building projects from that time until the mid-sixteenth century, this chapter reveals its importance in the organisation’s self-image: as an elaboration of the ritual, a demonstration of institutional pride, and as an instrument of display and propaganda. The level of detail provided by the continuous run of accounts is exceptional, and affords historically important insight into developments in instrument design over a 150-year period, from a single Blockwerk into a more sophisticated instrument with various keyboards, registrations and chests. The study also provides an exceptional level of detail on the complex process of scoping, ordering, building-work and quality control that went into the installation of an organ in a large church building in the later Middle Ages.