[Smt-talk] Irregular cadence and the circle of fifths progression

[Ninov, Dimitar N]

Dear Nicholas,

Actually, Rameau pointed out very nicely the two possibilities that you thought he was missing to combine together in his mind: 1) the II6-5 - I plagal relationship that he calls "irregular cadence" (on p. 74 of the English translation) and the most popular sequence in tonal music that moves in a circle of perfect fifths (with one diminished) and makes use of all diatonic chords in the major mode (and all diatonic and relatively diatonic in minor mode): I-IV-VII-III-VI-II-V-I (p. 255 in the English translation).

For me both principles are true and strong, and they do not negate each other: the fact that there is a plagal relationship to the tonic exhibited by the bass of the 4th scale degree; and the fact that the motion in descending fifths (or ascending fourths) is a powerful engine that may outline a key and make use of all diatonic chords in the mode. Hundreds of tunes from Baroque to nowadays have been composed along this sequential model. It is enough to open a Bach piece or to play Autumn Leaves or Fly Me to the Moon to experience the beauty of the sequence. Interestingly, the same skeleton carries so many different melodies and styles through the centuries, and it does not become obsolete!

With the the recognition of the motion of descending fifths, we have to also recognize the descending third motion, and the connecting stepwise harmonies that may or may not be a substitute for a stronger progression. The motion of ascending thirds basically represents a reversed syntax (except for I-III), but if it is stylistically justified, it does not sound "wrong". Also, Mozart simply loves to connect VI to I6, before an extended cadential progression: V-VI-I6 (some caesura) then IV (II6) cad. 6-4 - V7 - I. This connection (VI-I) is theoretically a reversed syntax, but the bass of VI relates to the bass of I6 as subdominant to tonic and it sounds as a progression, not a regression.

Best regards,

Dimitar

Dr. Dimitar Ninov, Lecturer
School of Music
Texas State University
601 University Drive
San Marcos, Texas 78666