rising to a D indicated a
particular progression and could be learnt as a formula; such scales as given
by Gasparini (L'armonico pratico, 1708/R) merely extended and codified
the practice.(It.: ‘rule of the octave’).
A
term used by certain 18th-century figured bass theorists to refer to a simplified
system of harmony in which each note of a diatonic scale (ascending and
descending an octave) considered as a bass part can be assumed to have its own
chord above. The ‘rule’ is thus a rough and ready guide, and a figuring such as
that in ex.1 (Rameau, 1722) is only one of several
possible. The idea is a practical one, and although the phrase itself occurs
late (in Campion's Traité … selon la Règle des Octaves, 1716) and
although some writers treated it somewhat theoretically (Mattheson, Heinichen,
Schröter, Blankenburg), figured bass players had long been accustomed to
thinking that certain bass lines probably indicated certain harmony. Many
17th-century theorists and composers had assumed, for example, that a C rising to a D indicated a
particular progression and could be learnt as a formula; such scales as given
by Gasparini (L'armonico pratico, 1708/R) merely extended and codified
the practice.
See also Continuo.
PETER WILLIAMS