Again and again, one discovers two patterns of movement yielding innovations in the history of European music: regional styles that were previously distinct from one another merge together in synthesis, as do stylistic tendencies that were previously tied to different genres. Both patterns may be invoked in an attempt to historicize the use of accidentals in a handful of important motets by Guillaume Du Fay, including Nuper rosarum flores and the troped Ave regina celorum. Historians have hardly been unaware of the importance of the influence of English music on Du Fay, nor have they been unaware of Du Fay's interest in transferring stylistic features from one genre to another. But it is useful to bring these two perspectives together, especially given the advance of recent scholarship. Our analysis may proceed from the basis of two well-known statements from the period. The first, from a treatise (c. 1400) attributed to the composer Philipoctus de Caserta, states that:
