Rule of the octave
The rule of the octave is a way of harmonizing each note of the diatonic scale, reflecting common practice, and has its origin in the practice of thorough bass, or basso continuo, where it provided an easy way to find which chord could accompany each note of the scale in the bass, particularly in the absence of figuring. The earliest description of the chords harmonizing an octave may be that by Antonio Bruschi in 1711.Gregory Barnett, "Tonal organization in seventeenth-century music theory." The Cambridge History of Music Theory, Th. Christensen ed. Cambridge University Press 2002, pp. 442-443. The name (règle des octaves, "rule of the octaves") was first given by François Campion in 1716.François Campion, Traité d'accompagnement et de composition, selon la règle des octaves de musique. See Joel Lester, "Rameau and eighteenth-century harmonic theory." The Cambridge History of Music Theory, Th. Christensen ed. Cambridge University Press 2002, pp. 756-757 The rule of the octave also formed the cornerstone of the "regole" (rules) of partimento collections.{{Cite web|url=https://wayback.archive-it.org/org-1018/20170928202917/http://faculty-web.at.northwestern.edu/music/gjerdingen/Partimenti/collections/Furno/regoleP2.htm|title=Scale Steps|website=faculty-web.at.northwestern.edu|access-date=2016-07-04}}. See [http://partimenti.org/partimenti/collections/furno/the_method_1817.pdf Giovanni Furno, Metodo facile e chiara.] There is normally a different harmonization for ascending and descending bass lines, and, although called a rule, there are several variants with different chords. Different versions for the major and minor scales are recorded.{{Cite web|url=https://wayback.archive-it.org/org-1018/20170928202539/http://faculty-web.at.northwestern.edu/music/gjerdingen/Partimenti/aboutParti/ruleOfTheOctave.htm|title=Regola dell'ottava|website=faculty-web.at.northwestern.edu|access-date=2016-07-04}}. See [http://partimenti.org/partimenti/about_parti/rule_of_the_octave.pdf Robert Gjerdingen, An Illustrated Guide to the Rule of the Octave.] One example for the major scale by John Hiles,Hiles, John (1882). A catechism of harmony, thorough-bass, and modulation, with examples, p. 82. (this expansion of Hiles' line contains consecutive fifths of the second and third voices between the sixth and the seventh chords; which can, however, be avoided by crossing these voices e.g. in a choral version):
\new PianoStaff <<
\new Staff {
\new Voice = "right" {
\relative c' { \clef treble \time 4/4
}
}
}
\new Staff {
\new Voice = "left" {
\relative c { \clef "bass" c4 d e f | g a b c | c b a g | f e d c |
}
}
}
\new FiguredBass {
\figuremode { <_>4 <4 3> <6> <6 5> | <_> <6> <6 5> <_> | <_> <6> <6+ 4 3> <_> | <2> <6> <4 3> <_> |
}
}
\new Lyrics {
\lyricsto "left" { I V I II | V IV V I | I V V/V V | V I V I |
}
}
>>