This paper addresses the complexity of being Greek Orthodox in the late nineteenth-century Ottoman Empire. It looks at questions of imperial belonging, supranational and national identities in the Ottoman Empire, especially focusing on its Greek Orthodox middle class. It explores how music relates to national, religious, and class identities in Stanbuliote Greek Orthodox urban groups in the nineteenth century. It treats identities not as singular, given, and constant categories, rather as multiple and in flux. The paper examines the entangled developments of those identities and the practices involved, within the context of the mid-nineteenth century imperial reforms and their impacts on the millets, the penetration of European patterns and Western cultural impact, and social class formation. To give an example, class and national identities were intertwined in the activities of the voluntary societies and associations which were founded by the Greek Orthodox middle-class. And music was significant both for the imagination and assertion of national identity, and for the articulation of class identity. In the last decades of the empire, hybrid, converging, and conflicting identities were part and parcel of the mixed and mingled populations of major Ottoman cities which some historians have tended to refer to as the phenomenon of ‘cosmopolitanism’. One of the aims of the paper is to open up a discussion over this term, and as opposed to the colonial or semi-colonial framework with which the term has been almost exclusively associated, to point to the internal and indigenous social and cultural fermentations which did not necessarily derive from an increased Western impact on the different levels of the society. As a remarkable space of hybrid practices, inter-communal interaction, collaboration and debate, the paper finally focuses on discussions over musical heritage between Ottoman Greek and Turkish musicians at the turn-of-the-century where inclusivist and exclusivist identity discourses met and clashed with one another.