Three ways to harmonize a note with a triad?

Question

For simplicity assume we're in C major. Let's say I'm playing a song, and I want to play a basic triad chord to harmonize whatever current melody note is played. In this example say the melody is a D note that I would play with my right hand. Then for my left hand, I think there's three possible chord combinations that I can play (I usually pick the one that sounds best):

1. The note is on the left of the triad
2. The note is in the middle of the triad
3. The note is on the right of triad.

Does this sound about right?

Edit: In this question I (incorrectly?) assumed the triad has to include the melody note. I haven't ever seen it not including the melody note, but maybe that's just due to my inexperience.

Answer 1

If by “C major,” you are assuming the key of C, with, as you explained in a comment, no alterations and no accidentals, and using the note “D” as a reference point, and if you are assuming a triad to mean only the adjacent diatonic intervals of 3rds (based on your graphic), then yes, what you have built is accurate. It is pretty fundamental to music theory.

Of course, this applies to any note in the scale, not just D. In C major, start on C, and you can have C be the root (C major), the third (A minor), or the fifth (F major); go to D, and the same applies; go to E, and the same applies; etc.

Your question more particularly seems to assume the constraint that the melody be part of the triad itself or be a note that is in common with a note in the triad. This need not be the case; indeed, it often is not the case. Melodies can be tricky, fluid things when you are considering harmonization.

Take the well-known “Auld Lang Syne,” for instance:

LilyBin link, with MIDI audio

In this very basic harmonization, even in the first measure, we encounter a melody note that does not “fit” into the triad of F major. In almost every measure, there is a melody note that does not “fit” into the triad that is harmonized with it.

On the other hand, if you harmonized every note in its own triad according to the rules in your question, it might arguably sound worse:

LilyBin link, with MIDI audio

The combination of melody notes that are part of the triad and that are not part of the triad is often what provides musical interest.

This is to say nothing, of course, of extending the harmony beyond triads—suspensions, extensions, and borrowed, oh my! But, given the constraints you provided in your question, yes, notes can be harmonized with any of the three notes in a diatonic triad of which that note is a part—but when harmonizing a melody, I think it is often advisable to know how best to produce good music. To only look for triads that “fit” the melody in the way you describe seems like an inadvisable course to stay on, but it is a good starting point.

Answer 2

There are actually more ways, many more ways.

One fairly straightforward way is to make the melody note the seventh of the chord. So in this case the chord would be E G B.

From there you could make the melody note an add 9 by using the chord C E G, but an octave lower, add 11 with A C E, etc.

Depending on how long you are playing the D and on what beat and whether it is emphasized or not, you could "harmonize" it with almost any chord. Each choice has a different flavor.

You could also borrow triads that contain D from related keys. And of course you could branch out beyond triads.

Answer 3

It's a very narrow question. But, within its terms, yes you're correct.

But that information isn't terribly useful. Because there are triads other than diatonic ones. And there are chords other than triads. And there are 'non-chord tones'. And all these are VERY commonly used, even in quite simple music.

But if you INSIST on "I want to play a basic triad chord" I can't argue with your logic.

Answer 4

That is right if you want an easy guaranteed harmony for a single note. When you consider music is a series of notes you also need to consider the sequence of chords you have and their relation to one another. It works playing several notes with the same chord, some that are in the chord and some that are not. Music that only uses "safe" harmonies tends to sound static and boring. Try holding down a chord and seeing how each note of the scale (or out of it)sounds against that chord. Some cry out to you to move them back or forward to a more harmonic note. If the next note of a melody does this it gives a feeling of tension then resolution giving a sense of dynamics in the tune. You can do this all by ear but it helps to know what the intervals between notes are so you can put a name on what you like to help remember it and duplicate it in another key.