Sample from the start of chapter 6: Note groups, Flourishes, and Trills: The developing language of notation
Composers throughout history have used the notation which they inherited to the limit of its capacity to convey information; but creative thought at times exceeded this capacity. In the past, it was common practice to leave some subtleties like changes in tempo during a piece to the performers sensitivity, sometimes aided by accepted conventions. In musical situations where conventions did not apply, or where the composer wrote with personal expectations which were more $nh{sophisticated} than those which players could readily grasp, even 18th century performers would probably have been forced to scratch their heads, or may have given a performance which missed the composers point.
As we might expect, the more subtle or spontaneous the musical thought, the more approximate the notation was likely to be. Decorations like flourishes and trills are essentially spontaneous. Where composers tried to write them out, a crude approximation often resulted, which was to be treated flexibly. Changes in notational practice over the course of time, together with the varied notational practice of different composers working at the same time, may also provide clues to the performance of some awkward motifs.
continues