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Consecutive Octaves by Contrary Motion


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#1 Vox Humana

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Posted 18 July 2013 - 21:45

Forgive me if this has been asked before, but I only pop in here occasionally and couldn't find anything in a quick look.

Standard wisdom has it that, in conventional harmony, consecutive octaves are illegal, whether the parts move in similar motion or in contrary motion (e.g. for the latter, two notes a fifteenth apart moving to an octave, or an octave moving to a unison - or indeed vice versa). I am, however, aware of a number of instances by some very respectable people who "knew their stuff" - Sir John Stainer, Haydn Keeton and G. J. Bennett to name three - who have harmonised a melody that ends by falling a fifth from dominant to tonic with a standard perfect cadence in which the bass rises from dominant to tonic, thus creating octaves by contrary motion. I have also seen examples by Sir Edward Bairstow and Sir Joseph Barnby which do the same in the opposite direction - the bass falling and the melody rising. All these examples are final cadences and, although they are technically incorrect, I really cannot see any better way of harmonising a melody that ends in this way since avoiding the perfect cadence would sound very contrived and unsatisfactory. At final cadences this progression must surely be allowable and clearly these very respectable harmonists thought so. However I was never taught this in my harmony lessons and I have never seen it sanctioned in any textbook (not that I am well read in such things). Does anyone know of an authority who specifically mentions this as OK?
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#2 Guest: Very Sane Tom_*

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Posted 19 July 2013 - 07:10

QUOTE(Vox Humana @ Jul 18 2013, 11:45 PM) View Post

Forgive me if this has been asked before, but I only pop in here occasionally and couldn't find anything in a quick look.

Standard wisdom has it that, in conventional harmony, consecutive octaves are illegal, whether the parts move in similar motion or in contrary motion (e.g. for the latter, two notes a fifteenth apart moving to an octave, or an octave moving to a unison - or indeed vice versa). I am, however, aware of a number of instances by some very respectable people who "knew their stuff" - Sir John Stainer, Haydn Keeton and G. J. Bennett to name three - who have harmonised a melody that ends by falling a fifth from dominant to tonic with a standard perfect cadence in which the bass rises from dominant to tonic, thus creating octaves by contrary motion. I have also seen examples by Sir Edward Bairstow and Sir Joseph Barnby which do the same in the opposite direction - the bass falling and the melody rising. All these examples are final cadences and, although they are technically incorrect, I really cannot see any better way of harmonising a melody that ends in this way since avoiding the perfect cadence would sound very contrived and unsatisfactory. At final cadences this progression must surely be allowable and clearly these very respectable harmonists thought so. However I was never taught this in my harmony lessons and I have never seen it sanctioned in any textbook (not that I am well read in such things). Does anyone know of an authority who specifically mentions this as OK?

The prohibition of parallel octaves is because it can make it sound like one voice has temporarily disappeared. Well what if the composer wants the effect of a voice disappearing?

There is no need for any "authority" to "sanction" anything you wish to do in a composition. There is (thankfully) no "harmony police" although there are plenty of control freaks that think that is their life's calling. If it is the sound you want, because it sounds good, or creates some other emotional effect that you want, then do it. The sound is primary. The so-called rules are partly theoretically based, but mainly follow what works in practice.
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#3 BitterSweet

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Posted 19 July 2013 - 07:38

Forgive me if I'm mistaken, but aren't all the composers you mention quite recent? I think, really since the early 20th century, there's been a rule of thumb in music that "everything is permissible, but not everything is beneficial".

Parallels are fine in a free composition if they're used for effect. They're just not ok to be used in harmonising a Lutheran Chorale. I'm sure I read that somewhere when preparing for my Grade 6 theory. I don't know where though.
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#4 linda.ff

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Posted 19 July 2013 - 07:42

How could you possibly harmonise a melody which ends soh-doh with a perfect cadence if you can't do it by contrary motion V-I? Only ever use a first inversion for the V chord? Or am I missing something?

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#5 Kai-Lei

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Posted 21 July 2013 - 13:12

Rules, rules!!! They were once guidelines to help would-be composers with musical taste. You'll find early polyphonists, Pergolesi among others, "guilty" of hidden 5ths but the instances I know about don't sound unmusical.

It's up to you. But with your arrangement, in 4-part harmony, you may end up with 3 roots and a 3rd on the final chord. The 3rd of V - leading note - may have to rise to the tonic depending what leads up to the V. If approached by Ic, the part that's on the tonic (in Ic) is effectively an appoggiatura, dropping to the 3rd of V and may then fall to the V in Ia - the exception about the leading note rising.

But I'm assuming you're A) you're writing in 4 parts and B) you don't want to end on unison octaves.
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#6 Vox Humana

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Posted 22 July 2013 - 12:14

Thanks for the replies. To be honest, I think I'm probably ahead of you here. Composition was one of my studies at the RCM, so I know the rules and, judging by what I see, I think (or, rather, hope) that I have a rather better idea about when and how to break them than most people. Stainer, Barnby and Keeton are in no sense modern composers; Bairstow has more harmonic originality, but is still, I would suggest, essentially a traditionalist. I tend to think of Vaughan Williams and Holst as the first British "moderns".

My query wasn't really about whether it is OK to use contrary motion octaves at a final perfect cadence. As linda.ff points out, it must be because every alternative way of harmonising such a melodic ending is inferior and the reason I cited the composers I did was to give some authority for this viewpoint. I was really just idly wondering whether any of the standard texbook authorities dealt with this. It's not the sort of thing you would want to risk doing in an exam, so I rather suspect they don't.
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#7 kenm

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Posted 23 July 2013 - 07:07

The first rule of species counterpoint is that the final must be approached by step in each part. If you break that one, it's not surprising to find that you need to bend some of the others.
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#8 ssngai

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Posted 24 July 2020 - 08:04

I came upon this rather old thread and happened to have what Vox Humana was looking for:

 

Harmony by Ebenezer Prout, Chapter III, section 69: "There is one exception to the prohibition of consecutive octaves. They are allowed by contrary motion between the primary chords of the key, provided that one part leaps a fourth and the other a fifth. A similar progression from the unison to the octave or the octave to the unison is also not infrequent between primary chords. Evidently this will be between two adjacent parts of the harmony, mostly tenor and bass."

 

You can find the text here: https://books.google...epage&q&f=false

 

I'm sure this isn't the only text that gives this exception. As Vox Humana noted, this sort of consecutive octaves by contrary motion is found not infrequently at the ends of phrases. If you don't allow this exception, as linda.ff noted, there is no satisfying way to harmonize a final 5-1 in the melody. The alternative, the first inversion 7-1, isn't very satisfying at a final cadence. I note that Bach did in fact use a 7-1 to harmonize the descending fifth in the end of the subject of Fugue #18 (g# minor) in WTK I, but then again one generally tries to limit the number of perfect authentic cadences in a fugue.


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#9 Hildegard

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Posted 29 July 2020 - 07:52

I'm sure this isn't the only text that gives this exception. .

 

Modern textbooks on harmony, such as Butterworth and also Benham, usually advise avoiding consecutive 5ths and 8ves by contrary motion. I think those who set exam questions for harmonisation tend to avoid melodies in which they would be the preferred solution.


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#10 Vox Humana

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Posted 03 August 2020 - 21:33

Excellent! I thought someone, somewhere would have mentioned it. Thank you so much, ssngai.   :)

Online version of the book here:  https://archive.org/...ge/n47/mode/2up


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