Quote:
Originally Posted by echurchill
Another way to keep the tonic note in the uppermost voice of the I chord is to descend from the supertonic. In this PAC, the root of the I chord is usually tripled, since the bass moves to the tonic, the leading tone should move to the tonic, and the supertonic moves to the tonic. When writing a chord with tripled root, usually the 5th is omitted and the 3rd is used instead. Cadences with supertonic-tonic in the soprano are in measures four through six. In the cadence of measure four, for example, the tenor moves down a 3rd to fill in the 3rd of the I chord with tripled root.
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I think that this point here led to your confusion about unisons. I think I should explain the role of unisons in this sort of chorale exercise. The role of unisons in real music is very similar too.
UNISONS
The unison is of course the smallest interval, and some authors even deny that it is an interval at all. Of course it doesn't matter at all what we call it. In exercises like these we seldom come across
unisons yet because we have restricted ourselves to root position chords with a doubled root. Thus the tenor and bass are the only voices that can meet in unison so far (For example, if the tenor and alto were in unison, the 3rd or 5th would be doubled). You should never hesitate to use this unison between the tenor and the bass as long as you are following all my guidelines concerning disposition (spacing) and doubling. Look at bar one and bar two of the UnisonExamples file. This sort of unison is always fine.
In my last lesson on cadences, however, I introduced a common cadential formula with a tripled root. A full V chord with doubled root can move to an I chord with tripled root; see bar three. The bass of the V leaps up a fourth or down a fifth, the 3rd (leading tone) and 5th (supertonic) of the V chord move up and down a step, respectively, to the root (tonic) of the I chord. Now extra doubled root of the V chord could be tied into the next chord like in bar three; if you listen carefully, however, the I chord sounds awkward and empty to classical ears because it is missing the 3rd. Bar four presents our solution: the 5th of the V chord can leap down by a third to the 3rd (mediant) of the I chord.
This tripled root often includes two notes in unison like bars five and six. Three notes in unison are also possible, though less appropriate like in bar seven.
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Also lets not forget that the I chord can also be approached with a normal
doubling when the leading tone is in the soprano. In this situation we are less bothered by the supertonic moving upwards like in bar eight.
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I hope that all this clears up the confusion from the last lesson. All the numbers and chords and scale degrees are easy to confuse, but if you read very carefully it should eventually make sense. Since this is very compressed teaching, every sentence I write is very important, so be sure to try them out on paper or Finale as you read. Of course we should not loose sight of the truth, that the exact handling of unisons is just a minor detail. The bigger picture will hopefully emerge once I teach the minor mode and inversions in the next few lessons. Exercises will be coming later today.
Also I hope that you continue to keep in mind that all these "rules" are relative. In actual music anything is possible and appropriate in the right circumstances. Following rules strictly in exercises, however, is excellent training.