which also circulated in church choir manuscripts with organ accompaniment. My Ladye Nevells Booke The 1580s were also a productive decade for Byrd as a composer of instrumental music. On 11 September 1591 John Baldwin, a tenor lay-clerk at St George's Chapel, Windsor and later a colleague of Byrd in the Chapel Royal, completed the copying of My Ladye Nevells Booke, a collection of 42 of Byrd's keyboard pieces, which was probably produced under Byrd's supervision and includes corrections which are thought to be in the composer's hand. Byrd would almost certainly have published it if the technical means had been available to do so. The dedicatee long remained unidentified, but John Harley's researches into the heraldic design on the fly-leaf have shown that she was Lady Elizabeth Neville, the third wife of Sir Henry Neville of Billingbear House, Berkshire, who was a justice of the peace and a warden of Windsor Great Park. Under her third married name, Lady Periam, she also received the dedication of Thomas Morley's two-part canzonets of 1595. The contents show Byrd's mastery of a wide variety of keyboard forms, though liturgical compositions based on plainsong are not represented. The collection includes a series of ten pavans and galliards in the usual three-strain form with embellished repeats of each strain. (The only exception is the Ninth Pavan, which is a set of variations on the passamezzo antico bass.) There are indications that the sequence may be a chronological one, for the First Pavan is labelled "the first that ever hee made" in the Fitzwilliam Virginal Book, and the Tenth Pavan, which is separated from the others, evidently became available at a late stage before the completion date. It is dedicated to William Petre (the son of Byrd's patron Sir John Petre, 1st Baron Petre) who was only 15 years old in 1591 and could hardly have played it if it had been composed much earlier. The collection also includes two famous pieces of programme music. The Battle, which was apparently inspired by an unidentified skirmish in Elizabeth's Irish wars, is a sequence of movements bearing titles such as "The marche to fight", "The battells be joyned" and "The Galliarde for the victorie". Although not representing Byrd at his most profound, it achieved great popularity and is of incidental interest for the information which it gives on sixteenth-century English military calls. It is followed by The