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I have heard that the I-V cadence is to be avoided when playing chant accompaniment, eg Gregorian chant.

It seems to me that the leading tone going to the tonic makes it sound like a tonal cadence rather than a modal cadence. Tonal music is based on the leading tone and modal music is not. I also never see or hear a melody in Gregorian chant that sounds like V-I.

Why is the V-I cadence to be avoided?

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It's not that Gregorian chant avoided the V-I cadence; it's that the chants were structured around entirely different concepts, and the V-I cadence did not yet exist.

There were eight Gregorian modes, each having an "authentic" and "plagal" version. The authentic mode was rooted on the "final" (analogous to the "tonic") and extended up to the octave. The plagal versions shared the same final, but extended from a fourth below to a fifth above. The below image illustrates the modes and their finals.1

Gregorian modes

The Dorian, Hypodorian, and Mixolydian modes sometimes extended one pitch lower, which, given the structure of those modes, would have been a whole-step. Thus the only mode leaving room for a leading tone in the Tonal sense would have been the Hypolydian.


Wikipedia has a good summary of the Gregorian modes and how they functioned. It would be a good starting place for further reading. The article on Gregorian chant is also useful reading. In particular, it discusses the construction of chant melodies. Brittanica also has an illuminating article on Gregorian chant.

An SE question that might be of interest:


1From Wikipedia: By Benjamin D. Esham (bdesham) - Created by bdesham with GNU LilyPond and post-processed with GraphicConverter. The original version of this image was made by Hyacinth. The fs in the image are those designated by Curtis as "final". The sources listed at that image page are Judd, Cristle Collins (ed.) (1998). Tonal Structures of Early Music. New York: Garland Publishing. ISBN 0815323883 Liane Curtis. "Mode"., Public Domain, https://commons.wikimedia.org/w/index.php?curid=63101

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Consider each mode, with regard to its 'leading note'.

Ionian has a semitone from notes 7>8.

Dorian has a tone.

Phrygian has a tone.

Lydian has a semitone.

Mixolydian has a tone.

Aeolian has a tone.

Locrian has a tone.

All except Ionian, which is tonal, and Lydian, have a true 'leading tone'. Maybe that ought to be a 'leading semitone'? Often termed 'leading note'.

So, the majority of modes don't actually have a true V>I. Not sure where that leaves Lydian.

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  • Lydian has the finalis on Fa. V-I is Sol-Do. A fifth above Fa is Do. We would have Do-Fa. Assume Fa is F. Then we would have Cmaj7-F. That wouldn't work, right? – user20754 Nov 12 '20 at 11:59
  • @Hank - In C Lydian (so Do is C like in your last chord progression), isn't Fa F#, not F? – Dekkadeci Nov 12 '20 at 13:05
  • The finalis in Lydian is Fa and not Do. If the finalis is the note F then that note is called Fa. This is what I was taught when I took organ lessons. – user20754 Nov 13 '20 at 13:04
  • @Hank - be aware that there are two different ways that solfege names are used. I guess yours is fixed do, where do is always the note C. The other is movable do, where do is the tonic of whatever key is chosen. So in key F, for example, you call F fa, others may call it do. – Tim Nov 13 '20 at 13:16
  • C is not always Do. F can be Do. If F is do then Bb is Fa. The finalis in Lydian would then be Bb. I use the movable Do. You must have had teacher who did not even know anything about chant theory. I have a piano teacher who are also confused about church modes. perhaps this is because jazz thinks of modes in another way than what we do in chant theory. – user20754 Nov 14 '20 at 15:32

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