Introduction and Acknowledgements Robert ap Huw (c.1580-1665), a harp-player and poet from Anglesey, was the maker of a unique manuscript of harp music (Lbl MS Add. 14905). This corpus of music, some of which has its roots in the thirteenth century, belongs to the Welsh tradition of cerdd dant ('the music of the string'), and appears to be quite distinct from the mainstream of European instrumental music in the early seventeenth century. But contemporary tune lists and a fragment of music copied out by Iolo Morganwg in 1800 (Lbl MS Add. 14970) suggest that the manuscript was typical of a larger group of lost sources, and certainly representative of a substantial repertory known in Wales during the sixteenth and seventeenth centuries. Robert ap Huw's manuscript therefore invites intensive exam- ination because of its unique yet representative status. It has attracted attention from antiquarians and historians since the eighteenth cen- tury, but it is only with the most recent research into the early harp, the modes of playing and tuning it, and the cultural, musical and literary contexts, that the problems implicit in understanding the source and its repertoire begin to emerge. A symposium held in 1995 by the Centre for Advanced Welsh Music Studies was the spur for this volume. However, it includes new research and thinking undertaken since then, and forms part of an ongoing collaborative project. There are studies of Robert ap Huw's background, the history of the manuscript, its repertory, associated composers, and compositional technique; the oral (and aural) trad- ition to which it belongs and the contemporary harp technique reflected in it, as well as the related Iolo Morganwg manuscript. Comprehensive indices, explanatory material, and a glossary which, though far from definitive, should assist with more obscure termin- ology, all provide a basis for further development. Robert ap Huw spent most of his life on Anglesey. Nevertheless, the silver crest on his best harp and a cywydd written in his honour by Huw Machno (c. 1560-1637) suggest that, like other Welsh musi- cians of his time, he may have worked at the royal court for at least a short period. Here he would have encountered the most fashion- able music played in court circles. None of this is revealed in his collection of Welsh harp music, which is both aesthetically and