ABSTRACT
The interpretation of fifteenth-century diminution signs is problematic. Theorists describe three types of diminution, all of which may be represented by the same signs: proportional diminution, which reduces the durations of notes in relation to other notes in the same piece; mensural diminution, which reduces the number of mensurae, or counting units, with which each note is measured; and accelcratio mensurae, which reduces the duration of the mensura itself. The writings that describe these procedures are often ambiguous and have been interpreted in conflicting ways. Clarifying the distinctions among the categories of diminution helps to make sense of problematic theoretical statements and resolve apparent conflicts between theory and practice. Since most theorists apply the concept of proportional diminution only to simultaneous relationships and acceleratio mensurae probably arose no earlier than the 1460s, mensural diminution is the principal theoretical meaning of diminution signs in the first half of the fifteenth century. Placing the reformist ideas of Tinctoris and Gaffurio in the context of earlier theories leads to new interpretations of their views on diminution. Their struggles to resolve the conflicts between traditional practices and their own rigorously rational systems led to inconsistencies that laid the foundation for the controversies that have plagued interpretations of diminution signs ever since.
