The cultivation of high-art polyphony has always been the preserve of a cultured elite minority who could write, read, and sing it. In the early fifteenth century, the number of surviving books significantly increases, facilitating insights into the geographical spread and longevity of the repertory, how and for whom books of music were made, even matters of authorship and performance. English music has many threads linking it to other collections within England and on the Continent. After centuries of only fragmentary survivals, the fifteenth century brings several more or less complete English manuscripts along with a rich harvest of fragments. Fourteenth-century notation uses filled black notes, with mensural or proportional differences shown as void or red notes towards 1400. The distinction between institutional or commissioned manuscripts and personal compilations corresponds closely to dimensions, discounting different sizes of writing block within a manuscript.