In Western Europe, Muslims are increasingly demanding the right to amplify the Islamic call to prayer, the azan. Local resistance to the azan has prompted a search for technologized alternatives, of which architectural proposal to use light signals instead of loudspeakers is the only public alternative. By describing the light-azan proposal in the Netherlands, followed by an analysis of the extent to which it has been actually adopted, its association with spirituality is investigated from the perspective of mosque aesthetics negotiations. Aesthetic technologies of ordering physical spaces, in this case a transduction of sound into light, but also the use of glass in mosque architecture, can regulate the extent and quality of Muslims’ presence in European cities. Whether the medium of light can faithfully convey the human voice, however, is bound with questions of religious authority.