‘My Lady Nevell's Book’ is one of nearly thirty manuscripts, mostly dating from the early seventeenth century, which contain keyboard music by Byrd. Unfortunately none of them is in the composer's own hand, and naturally they vary greatly in reliability. There is also the one printed source, Parthenia, dating from 1612–3. This, as one might imagine, is more accurate than any manuscript source, but it contains only eight of Byrd's pieces. My Lady Nevell's Book, on the other hand, contains 42 pieces, all of them by Byrd—that is to say, about a third of his surviving keyboard music. The copyist was John Baldwin of Windsor, who completed his task on 11 September 1591. Among the sources of Byrd's keyboard music, the Nevell book is outstanding in a number of ways. First of all, it is the earliest dated source; indeed, among the undated manuscripts only one is certainly earlier than 1591, and that ascribes but a single piece to Byrd. It is also the only virginal manuscript of any size to be devoted to the music of one composer; furthermore it appears to include all the important keyboard works that Byrd had composed up to that time. Alone among surviving virginal manuscripts, it was intended to be presented to an aristocratic patron, and three of the pieces in the book were composed expressly ‘for my ladye nevell’ herself. The book is exceptional also for its calligraphy. Baldwin was a most careful and conscientious scribe, and, as E. H. Fellowes remarked, no praise can be too high for the beauty of his penmanship.