- Roger Bowers
A system (or systems) of graphic devices in musical notation, by the application of which the durations ostensibly prescribed for notes conveyed by pre-orthochronic notations were modified and made greater or less in accordance with a specified proportion.
Such graphic devices fall into two principal classes. First is coloration (or blackening): somewhat simplified, this may be described as the blackening of notation otherwise void, or – prior to the adoption of void notation – the execution in red full (also, rarely, red void or black void, even blue full) of notation otherwise black full. Second is the graphic modification of any of the four standard mensuration signs, either through its inscription in mirror-image or through the addition of a stroke and/or a number (or pair of numbers). The apparent note values could be either reduced in value or augmented; diminution was by far the more common. Resort to these devices is found in notation from the early 14th century to the early 18th, but enjoyed three particular periods of favour among composers: ...