This thesis develops an analytical approach to the instrumental music of Orlando Gibbons (1583-1625) based on close readings of historical theory sources, primarily by Thomas Morley, John Coprario and Thomas Campion. Music of the early seventeenth century can be difficult to analyse, since it falls between the more extensively studied and theorised practices of classic vocal polyphony and common-practice tonality. Although English music theory of this period is recognised as strikingly modern in many respects, innovative aspects of English compositions from the same period receive little attention in standard accounts of the seventeenth century. I argue that concepts taken from this body of historical theory provide the basic terms of a technical vocabulary for analysis, which should be further refined through application to real compositions. Successive chapters deal with common counterpoint models or patterns, imitative invention and disposition, cadential progressions, and overall tonal structure. I argue that these analyses show Gibbons's music to be a contribution to new ways of conceiving of instrumental polyphony and tonal structure, which deserves re-evaluation in the context of broader seventeenth-century trends. In particular, Gibbons's use of extended cadential expectations as an expressive element, fascination with sequential progressions, and sectional structuring by harmonic area have clear parallels with later practices. At the same time, early seventeenth century style allows the composer considerably more freedom of harmonic procedures and implications than the musical styles which immediately followed it. Analysis grounded in historical theory provides the best approach to understanding and appreciating this unique musical language.

English publisher John Playford (1623-1686/1687) first published his "The Division Violin: Containing a Collection of Divisions Upon Several Grounds for the Treble-Violin" in 1684. The first edition of this violin collection contains 26 written-out examples of improvisation, serving as a living snapshot of the performance practice of the time. This research is based on the second edition, which Playford had expanded into 30 pieces for the violin, published in 1685. The purpose of this study is to investigate the art of improvisation in England during the late 17th century, focusing on Playford's "The Division Violin." The dissertation first surveys the development of English violin music in the 17th century. Then, the dissertation traces eight selected 16th-century Italian diminution manuals. This will help readers understand the progression of the Italian diminution and improvisation practice in the 16th century and how it relates to the English division of the 17th century. Finally, based on a thorough research of the 17th-century improvisatory style and rhetorical approach, the author of this study provides performance suggestions on "Mr. Farinell's Ground," No. 5 from "The Division Violin."