The National Library of Greece (Ethnike Bibliothike tes Ellados) is one of the richest depositories of Byzantine musical manuscripts and is surpassed by its holdings in Greece only by the multitude of manuscripts found in the monasteries of Mount Athos. In spite of being such a rich archive, the National Library has never published a catalogue of its musical manuscripts - not all of which are Byzantine or Greek. It is the purpose of this catalogue to recover or, in some instances, to present for the first time the repertory of the musical sources of the library. This project has been twelve years in the making for Professor Diane Touliatos, involving the discovery and detailed cataloguing of all 241 Western, Ancient Greek, and Byzantine music manuscripts. Not all of these are from Athens or modern Greece, but also encompass Turkey, the Balkans, Italy, Cyprus, and parts of Western Europe. This variety underlines the importance of the catalogue for identifying composers, music and performance practice of different locales. The catalogue includes a detailed listing of the contents as written in the original language as well as the titles of compositions (and/or incipits) with composers, modal signatures, other attributions and information on performance practice. Each manuscript entry includes a commentary in English indicating important highlights and its significance. There is a substantive English checklist that summarizes the contents of each manuscript for non-Greek readers. A bibliography follows containing pertinent citations where the manuscript has been used in references. There is also a glossary that defines terms for the non-specialist. Examples of some of the manuscripts will be photographically displayed. The catalogue will enlighten musicologists and Byzantinists of the rich and varied holdings of some of the most important musical manuscripts in existence, and stimulate more interest and investigation of these sources. As such, it will fill a major gap in the bibliography of Byzantine chant and other musical studies.