The years between 1660 and 1697 were possibly the most decisive in the history of St Paul's Cathedral. Even the dates themselves are significant - markers for what had been and what would follow. For it was during this time that St Paul's was transformed, outwardly and inwardly -a process that pulled in its wake the music and musicians whilst many of the changes can be understood without reference to the music and musicians, they themselves cannot be understood in isolation. In 1660 the Cathedral stood alone. Its singers and much of its music were heard only there, and it had little contact with the other main choirs in London - of Westminster Abbey and the Chapel Royal. But the destruction of the building, and its replacement by a new, specifically Anglican cathedral brought about a change in its position. This is reflected in its music and musicians, which gradually lose their Cathedral flavour, and, by 1697, have begun to acquire a London, and indeed a national identity. This thesis offers an investigation in to the process of change, as seen through contemporary writings, records and music sources. Such documents are examined and compared with their counterparts from other establishments, in order to define the relationships and assess the process of change. Study of the music sources includes an extensive examination of the two most important from this period, that is the first edition of James Clifford's Divine Services and Anthems (1663), and the seventeenth-century artbooks in the Cathedral (MSS 259-60 and 261 a-263). Their significance as Cathedral sources is examined; and the dating of the partbooks - with its implications for choral services - is evaluated, and current thinking ultimately challenged. It is also suggested that LbI Add. MS 29289 was in use at the Cathedral during the early Restoration and that it provided a model for John Barnard's The First Book of Selected Church Musick (1641). Two other related manuscripts, Mp MS 340 Cr 71 and Lbl Add. MS 29430 are examined and considered as possible Cathedral sources.