cadences with triads with two different notes

Question

Can a cadence consist of a triad with only 2 different notes? Let's say I'm in Fmaj and want to include an imperfect cadence (ii - V): G - D - G followed by C - E - G. The first triad has only two different notes (G and D), is this possible?

EDIT: My question arose because I'm doing an exercise that requires writing a short melody ending in an imperfect cadence in Fmaj. I decided to use the ii-V cadence with the chords shown above. However, when I played the excerpt and finished with the "imperfect" cadence, it sounded a lot like a "perfect" cadence - the roots of the chords are G and C which are also in the perfect cadence in Cmaj and all notes are also present in the Cmaj scale. It certainly doesn't sound imperfect, which is why I was wondering if this would be allowed in music.

Answer 1

For a start, if a chord has only two notes it isn't a triad. It might IMPLY a particular triad, or be viewed as an incomplete triad. But a triad has three notes.

The example you give is certainly possible. In an F major context he bass notes - G, C - clearly outline a ii, V cadence all by themselves. Omitting the 3rd of the first chord means it isn't fully defined as G major or G minor, but that doesn't negate the overall shape.

If we're talking about 'harmony exercise' SATB writing, we must consider whether dropping into 3 part texture for one chord is effective. If we're writing in a more contrapuntal style, this sort of thing happens all the time.

Answer 2

For the cadence from Gmin to Cmaj:

Ommiting the third (Bb) of Gmin would make it Gind as it is "indeterminate". It is arguable whether a cadence can have the third ommitted because it makes it extremely weak. I could also find no cases of such a cadence. Furthermore, this would mean that it is also not an imperfect cadence.

So while this is possible, its not very strong.

To avoid large jumps in the treble voicings, here is an example of how to do it in terms of voice leading:

• S: D - C
• A: G - G
• T: D - E
• B: G - C

Answer 3

Yes, it's possible, like Tim says.

In early counterpoint it was even the rule that the final chord has no 3rd - in purpose to end in a perfect tonic. Even by Bach we can find still this practice.

There are 2 voice-canons missing the full harmony if sang without accompaniment like this one: youtube.com/watch?v=AGrsasgsFuQ

My question is: do we still speak of a cadence if there is only a single tune? but we could hear the chord progression I-IV6-V7-I ???