I've been listening to a lot of impressionistic and avant-garde jazz music lately. When choosing chords in a tonal, diatonic concept, the formula is somewhat clear to me. If it's a note in the scale, choose I, IV or V if in doubt. If it's a chromatic note, choose a secondary dominant, neapolitan chord or an augmented 6th, and maybe use the chromaticism as a point of modulation, if that's what you are going for. Sure there are lots of other ways to harmonize a melody in a functional setting, but I think these are the basic tools that classical and romantic composers used. In jazz, I can somewhat understand the concept of passing chords and chord substitutions.

But coming to impressionism and modern music, where functionality isn't necessarily the goal anymore, how did eg. Debussy choose chords to his music? I see he uses lots of whole-tone scale and doesn't always resolve the lines the traditional way, but when I try to compose in his style, I find it difficult to think out-of-the-box. If I come up with a Debussy-like melody that is chromatically all over the place, I don't know what chords I should choose beneath it.

What principles are there for harmonizing a chromatic melody, other than just trying out if something might work?

  • 1
    A melody doesn't have to have a chord beneath it. It could have nothing, a note or notes from a previous harmony, or a single note, which can be ambiguous if you like.
    – Tim
    Dec 17, 2020 at 10:59
  • 1
    I recall that Debussy uses parallel chords more often than usual.
    – Dekkadeci
    Dec 17, 2020 at 13:10
  • 2
    Are you specifically interested in the techniques of the Impressionists? There are numerous methods for harmonizing non-diatonic/chromatic melodies - some include non-functional harmony, but they can also be harmonized by functional methods. It might be helpful to narrow the question a bit.
    – Peter
    Dec 17, 2020 at 14:24

4 Answers 4


I would say, to best understand harmonization of all music, it would help you to move beyond this concept:

When choosing chords in a tonal, diatonic concept, the formula is somewhat clear to me. If it's a note in the scale, choose I, IV or V if in doubt.

I suspect that most songwriters and composers are not at all thinking like that. It's not like they have a melody and they are just searching for chords that work with it. It's that the melody and chords work together to say what they want to say, and only one chord is the right chord for that statement combined with the melody note.

For me, it was Leonard Bernstein who helped me understand this by drawing an analogy between the notes of the melody being like nouns and the chords/harmony being like adjectives.

Suppose a melody note is like the noun "apple". Then you can talk about different kinds of apples by changing the harmony supporting the note. Like a red apple, or a rotten apple, or a poisoned apple, or a Cox's Orange Pippin just like your mom used to bring home from the orchard in early fall when you were living in upstate New York at the age of seven.

So even in diatonic composition, we would have a very small musical vocabulary and we wouldn't be expressing ourselves well if we A) had "doubt" about what chord to use and B) pretty much kept to I, IV or V because of that doubt.

Obviously there are many effective, evocative songs that only use I, IV, and V, or even simpler harmonizations. Two things: Sometimes the musical equivalent of baby talk is exactly what is intended, either to highlight the universal and ageless nature of the message or to leave the listener able to focus on lyrics or something like that. Secondly, even when the harmony for a piece is very simple, often the melody that goes with that harmony is all the more complex. I think delta and Chicago blues are excellent examples of very straightforward harmonies backing subtle and not quite diatonic melodies.

So that suggests approaching your question from the opposite direction. What if we asked, "How can one make a chromatic melody work over a I - IV - V chord progression?" Well, that's kinda like what blues is!

If you have a keyboard instrument or some ability to do so, I highly suggest playing or programming a single chord to repeat or sustain, and then slowly play a chromatic scale above that chord, listening for how each note of the scale interacts with the chord. Don't listen for whether the notes "work" or if they sound "right" or "wrong" with the chord, listen to how everything sounds together and what kind of feel you get from it. It can be very interesting to continue the scale an octave higher than you started it, to see how the distance between the "melody" notes and the chord makes a difference.

So really, any chord can be used under any melody note, as long as it supports the musical message and fits into the overall context.

Beyond that, chromatic music can be written either semi- or fully contrapuntally, where there isn't as much of a harmony/melody distinction, but intertwining passages that form both a melodic and harmonic picture. And there things like chord planing/parallel chords (as mentioned in the comments) where the chords are kind of playing the melody.

To summarize, I think it would help you immensely to try to reset or transcend the notion of "writing a melody and then finding chords that fit with it". Perhaps a good first evolution of that idea is "writing a melody and then thinking about each note of that melody and what 'adjectives' best modify that note".

Another way to break out of the melody/chord concept of composition is to write a melody, then write a bass line that you like along with the melody, and then add a third line in between them. And/or mix up the order in which you write them. And definitely think about each of the three lines of music standing on its own (e.g., don't let yourself write a bass line that is just the same note for three measures and then a different note for the fourth).


My interpretation of your question leads me to think that you are attempting to extend homophonic harmony principles to more "textured" melodic themes. This may not be the way to go. The basic rules of classical homophonic harmony, as you have correctly stated, are choose from the set (I, IV, V, or V7) based on the melody note.

When you have chromatic passing tones you need to think about how they relate to the original key, as they may serve a specific function. For example an augmented 5th in a major key would almost certainly feel like a modulation to the relative minor key via harmonic or melodic minor. So I might choose to play the III7 chord. Another example would be the presence of a flat 7th in the original key, indicating movement to the IV, not just a chord change but a true modulation. For that I would pick I7 moving to IV. But these choices depend on the melody as well. The chords need to enhance the melody by respecting the context.

There are other approaches to this and homophonic harmony is just the beginning. Most music doesn't even follow this procedure. In modern music the rhythm parts don't necessarily move with each and every note change. Take for example a classic Pat Martino guitar lick (borrowed, I am sure, from his predecessors)

{b3 - 3 - 4 - #4 - 5 - 3 - 1} + {b7 - 6 - 9 - 6 - 5}

The second part is just an extension of a 7th chord, specifically a 13th. The first part is a straight chromatic run up the "Blues" scale. This entire line would fit over a 7th chord with no modulation what so ever. What matters is the overall structure of the melody, the motive, the theme, and whether you sense that movement is really necessary or justified.

As for using the whole tone and other scales you have a couple options. One is to try and understand how that scale fits into or overlaps diatonic scales, like whole tone and lydian (which is 1/2 a whole tone scale). Keep in mind that the chords we use in harmony exist within the scale we use for melody. You could simply construct chords from the scales you use and see what emerges. However this really only makes sense (if at all) when your melody is entirely within the non-diatonic scale. Another approach is to see if your melody borrows occasionally from these non-diatonic scales but walks back into the diatonic realm. Then I would not be inclined to try and harmonize each and every specific note but treat them as passing tones, non-diatonic extensions, etc. Or don't harmonize at all like Tim mentioned in his comment. There are many scales in other cultures, like Indian music, that do not lend themselves to western style harmonization. It may be that there is no natural extension to homophonic harmony.


This answer requires a brief premise:

I have been developing training software for musicians for many years, and one project I worked on for some time (years ago, never released) included a function that generated random melodies (both diatonic and randomly chromatic) and then selected some chords to go with them.

When it came to writing the algorithm for selecting chords to go with random melodies I experimented with a variety of approaches, and here I'll partly describe one of them which worked reasonably well. Perhaps you'll find it useful in practice or interesting from a theoretical point of view.

Now, in short, the algorithm works like this:

  1. Every note in the melody receives a "weight" based on its position: Notes on strong down beats (1 and 3) have the highest weight. Notes on weak beats (2 and 4) have less weight. Notes on up beats (e.g. 8th note on the "and" in solfege) have even less weight, and 16th notes on position 2 and 4 of a quadruplet have the least weight.

  2. Generate chords whose notes total the maximum weight, adding the weights of the notes in the melody.

  3. Choose a sequence of chords where going from one chord to the next doesn't jump around too much (i.e. some notes are often in common between one chord and the next)

In other words, chords that may sound good on your "random" melody will be chords that include many of the notes on the strong beats (1 and 3), and to a lesser extend on beats 2 and 4, and to a still lesser extent, any other notes.

I think that can be a good starting point, and from there you can make your own changes and adjustments based on personal taste, style, etc.


...what chords I should choose beneath it...

...What principles are there for harmonizing a chromatic melody...

Certainly you can start with a melodic idea and then harmonize it, and that is a common exercise in harmony/counterpoint studies. But, at a certain point a more integrated approach what you learn, where you work with the whole tonality and texture. You might "sketch" out the harmony or simply hear it with your "inner ear", but you're working with it from the initial steps of composition.

how did eg. Debussy choose chords to his music?

First expand your chord palette to get familiar with a variety of seventh chord including non diatonic chords. Think less about root progression and more about voice leading, especially voice movement by half steps. Recognize and exploit tonal ambiguities, use tonal elements but reinterpret their meaning in different harmonic settings.

Consider this from Debussy's Little Shepherd...

enter image description here

It's really clear that it is a minor tetrachord (a tetrachord is four scale steps encompassing a perfect fourth, very significant is scale construction.) The key signature of three sharps suggests other wise, but it could be a B minor tetrachord and could be harmonized with Bm:V6 i. The F natural also wouldn't fit B, but for the moment let's consider it as just a neighboring embellishment and say we initially have a simple tonal element, a minor tetrachord. But the music actually harmonizes that passage three different ways and none of them treats it like a minor tetrachord!

First it gets a treatment strongly suggesting a whole tone scale...

enter image description here

Then it seem to put it in A and the three sharps key signature starts to make sense. It moves to an A major chord where the initial note of the treble C# is the chord's third...

enter image description here

Later it is transposed and the initial chord is an inverted minor chord and the initial treble of E# is the chord's fifth...

enter image description here

Before examining those three in greater detail the thing to notice is all three take the same tetrachord figure and harmonize it three totally different ways, and none treat the bottom note of the tetrachord like a tonic.

Also, let's look at a few other important harmonic points in other places.


enter image description here


enter image description here

...that's almost like Em: i V6 followed by Em: v(min) i. At first glace it's tempting to analyze the treble tones - is the E minor chord Em6 or Em7? - or note the chromatic change of D from sharp to natural - but what I think is more important is after all the preceding chromatic and ambiguous seventh chord stuff are these root progressions by perfect fifths.

The passage at m.9 actually extends the progression by fifths...

enter image description here

...which of course finally makes the key signature sensible! And then that passage is repeated in transposition later...

enter image description here

...and the transposition is up a perfect fifth. The preceding passage - m.12-15 - introduces a D# which added to the three sharps key signature gives us E major. It wouldn't make sense to talk about this as if it were a move to the dominant like in a sonata, but it brings the music back into a very tonal, diatonic context.

If you want to harmonize like Debussy, you need to both reinterpret musical elements in a very chromatic, non-traditional way without completely abandoning traditional tonality.

There are lots of things you can do to get the sound of Impressionism. From the examples above two things to try:

  • Voice lead seventh chords: hold two tones, move two. Use half steps, look for opportunities for half-diminished and dominant seventh flat five chords. Within the collection of tones for the two chords look for small diatonic segments (ex. tetrachords) for melodic development.
  • Use diatonic progressions by fifths but with "modal" flavors, try adding diatonic sevenths to these chords.

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