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Let's say I've written a song with the chord progression I-IV-V in the key of A (just as an example). So, the chords I'm playing are A-D-E. When playing a lead over this rhythm, what notes do I need to stick to over each chord? That is, when playing an A chord, should I stick to the notes that compose the chord? Are there rules for which notes sound good over which chords? When I move to D, are there notes I should avoid or continue?

I'm asking because I have a melody I like and I'd like to back it with rhythm guitar, but I'm not sure how to choose chords (basically the other way around from how I asked the question, but I'd like to know both). I'm just starting to learn musical theory and I'm not sure the best way to phrase my question.

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There isn't one definitive answer to this question besides "Try to be Paul McCartney." That said, here are some guidelines that I hope prove helpful:

Mix It Up

Don't just use chord tones (meaning, notes that are in the chord you're playing at the moment) and don't just use non-chord tones. Non-chord tones will give your melody a sense of momentum and tension, while chord tones will give your melody a sense of stability and release. Of the chord tones, roots and fifths have the most stability, while thirds and sevenths strike a nice balance. Too much of either is no good: too much tension and momentum, and you run the risk of your melody running out of control, which ultimately feels chaotic. Too much stability, and your melody will sound dull and boring.

Voice Leading

This basically means that your melody shouldn't jump around too much---a few big intervals are fine and can be really dramatic, but most of the time, your melody should stick to stringing together notes that are near each other. Otherwise it's hard for the listener's ear to keep up.

For example, say you're playing the A-D-E chord progression you mentioned. C# is the third of the A chord, and D is the root of the D chord (obviously). So a melody that plays the C# and then the D is employing voice leading.

Choosing Chords

So you have the opposite challenge: to pick chords to fit a melody. As before, there's no one right way to go about this, but again, here are some guidelines:

  • Identify the notes in the melody that feel more stable as opposed to those that feel as though they have momentum and movement and use those to help inform your chord choices.
  • Identify the few notes with the most drama. These probably shouldn't be chord tones, but might resolve to chord tones.
  • Chord progressions have their own momentum and stability. I chords are stable; V chords have momentum. You resolve a V (or V7) chord to its corresponding I chord. Unless you absolutely know what you're doing, make sure your V chords resolve or the song will leave your listeners feeling unsettled.

Example: "Eleanor Rigby"

"Eleanor Rigby"---"Rig" and "by" are both chord tones, and the melody lands on "by" like a rock. That note is the root of the chord, and it provides a lot of stability for the melody, which is good because the next line is...

"Picks up the rice in a church where a wedding has been"---"Rice" and "church" aren't chord tones, and they have a lot of momentum. This line is almost like a roller coaster: "Picks up the" is the initial ascent, followed by a briefly held point of tension on "rice", then a quick fall, a quick rise, and then another briefly held point of tension on "church", another fall, etc. It ends on "been", which is a chord tone for the next chord (the IV chord). Stability and release after the tension and drama of the roller coaster. Paul knew what he was doing.

I could go on, but it would take a long time, and this the main idea. Good luck, and enjoy the adventure of composition!

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  • I like this one. I've gone as far as putting some chords behind "Twinkle Twinkle Little Star" once, but this takes it a step past. Good answer.
    – Dave Jacoby
    Mar 17, 2011 at 2:10
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    I will try my hardest to be Paul McCartney, thank you! Seriously, though, this is great exposition of that simple exhortation.
    – Anonymous
    Mar 17, 2011 at 15:43
  • Great example :)
    – user28
    May 28, 2011 at 16:08
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I am not very good at theory, but I will leave my observations here. There are a few ways to approach this problem:

Got melody, want chords

  1. Figure out the key in which your melody is in.
  2. Figure out the triad chords can you play in that key (for example Cmaj/Amin key: Cmaj, Dmin, Emin, Fmaj, Gmaj, Bdim).
  3. Carefully check your melody and use the chord based on the dominant notes, usually this is simply the note which is played on the beat. So, if my key is C and the melody has a note D when the beat comes, I play Dmin, but also note that most of the time more than one chord sounds good in a particular situation.
  4. Don't stop when you got the chords, give them a twist (another note, different rhythm, a few notes connecting chords), using simple triads won't sound very innovative.

Got chords, want melody

  1. Figure out your key, this is essentially matching the notes in your chords to a key in which those notes are possible.
  2. Now you know the key and the notes you can play in that key.
  3. Try to move in this key, first follow the chords.
  4. Deviate from the chords and try to make it sound good. Unfortunately, there really is no recipe for writing melodies.

Alternative method

  1. Let the chords/melody repeat.
  2. Experiment until you are happy.
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I know this thread is old, but for people who find it via Google I want to add this article. It is fairly easy to read (theory-wise) and well researched.

David Temperley, The Melodic-Harmonic Divorce in Rock http://davidtemperley.com/wp-content/uploads/2015/11/temperley-pm07.pdf

The gist of the paper is rock music has two melodic modes: one where the melody tones agree with the harmony in a traditional way, and a second where the melody moves independently of the chords. It will take you several steps beyond a typical 'how to write a pop song' method of matching melody to chord tones with some embellishing non-chord tones.

This is solid music theory analysis with zero condescension toward rock music.

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  • Link is broken. This response would be better as a comment to the question.
    – peacetype
    Aug 26, 2020 at 15:46
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    @peacetype, DOI, but you might hit a pay wall doi.org/10.1017/S0261143007001249 I updated the link too, but you can just Google the title
    – Michael Curtis
    Aug 26, 2020 at 17:23
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Most modern music uses a slightly simpler version of something called “chord-scale theory.” In this system, melody notes that are “allowed” are determined by the scale. If a chord does not contain any notes from outside the scale, you could play any notes from the scale over the chord. In this case, all of the chords are inside the scale, so you would just play notes from A major.

This is not always the case. For instance, a somewhat common chord progression is C,E7,Amin. E7 contains a G#, which is not in C major. In chord-scale theory, if there’s a note in the chord from outside the scale, that note replaces the note in the scale. So in this case, you would play in c major with a G#.

There’s also a some concepts to be aware of called “guide tones” and “avoid notes”

Guide tones are notes that sound good over a chord, usually the 3rd and 7th. Over the A chord in your example, these would be C# and G# (with the G# being borrowed from the scale). Over the E chord, these would be G# and D (with the D being borrowed from the scale).

Avoid notes are notes that sound extra dissonant over a chord. This involves any note that isn’t either on a chord tone or a whole step above one. In your example, that would be a D over the A chord, or an A over the E chord. These are generally avoided or played quickly.

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The buzzword your question dances around is voice leading. Look that up in your textbooks.

The literal answer to your question is "there may be no relationship at all." For example, Bach's "Goldberg" variations include a few dozen instances of the same chord progressions (rhythm chords), each with wildly different melodies.

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When a chord is being played along with a melody, most melody notes which aren't in the chord will create "tension" and will want to move toward one of the chord tones (generally the nearest). When a melody moves from a chord tone to a non-chord tone, tension will significantly increase; when it moves from a non-chord tone to a chord tone, tension will significantly decrease. While some chord tones may have a little tension associated with them, and so movement between chord tones generally has only a minimal effect on tension.

Much of what makes music interesting is the creation and release of tension. Some pieces of create tension at the start of each measure and quickly resolve it, while others release tension and the start of each measure but then quickly impose it again. In many cases, even playing the melody unaccompanied may create sense of tension and release; in melodies where that is true, one should generally try to place chords so that they fit the "non-tense" notes in the melody. If a melody doesn't have a clear sense of "tense" and "non-tense" notes, it may be necessary to experiment. Some melodies can be harmonized so as to create either a "tense-relax" or "relax-tense" pattern.

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  • I'm perplexed does a composer have all this in mind when he composes?
    – Nachmen
    Jan 20, 2016 at 9:54
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    @Nachmen: A good composer should generally have in mind an intended pattern of tension and release. Some melodies have strong patterns of tension and release built into them, but many are fairly weak in the absence of surrounding chords.
    – supercat
    Jan 20, 2016 at 17:49
  • What I was thinking he composes a song then he works out the score whatever it is. But doing it the opposite way or together is something new for me.
    – Nachmen
    Jan 20, 2016 at 18:33
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    @Nachmen: Some melodies stand alone just fine, but there are some songs where the melody line really would be nothing without the backing chords. The song "I got lost in his arms" [Annie Get your Gun] has a melody which (key of D) starts "d d D, d d D, d d D d E, e e E, e e E, e e E e e F#, g g G, g g G, g g G g A" [each letter is one syllable; uppercase letters mark chord changes]. I can't imagine Irving Berlin having composed such a melody without having a harmonization in mind because there would be nothing to it--just a bunch of syllables on the first five notes of an ascending scale.
    – supercat
    Jan 20, 2016 at 18:45
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When I'm improvising harmony to a melody, I 5th chord tone track the harmony notes of the melody (usually the 1st and 3rd beat notes of each measure) except for Resolutions (I chord)at the end of verses, Turnarounds(V7 chord) to set up next verse, and Break (I7 chord) to set up the Bridge. Also, since most Bridges start on a IV chord and end on a V chord, those are what I use to start and end Bridges. I call this "5th Chord Tone Tracking".

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Here’s my response to the StackExchange question “Decide which chord to use”:

Given that I, IV and V chords often work for most melodies, it is far easier to apply this same idea in the following manner: play the root notes at 1, 3 or 5 note intervals BELOW each melodic note played on the main down beats. These three melodic-bass note intervals will work for a large majority of the time, particularly for simple songs. Most of all, you can use this simple scheme to identify the root notes by simply looking at and mirroring whatever note you’re playing on the right hand (with little or no mental effort).

To find the chord, play the bass note and the notes at 3 and 5 note intervals ABOVE the bass note (or 1-5-10). After playing three or four simple songs (e.g. traditional xmas carols) - preferably all in the key of C or C minor - you’ll quickly learn which melody-bass note intervals (including other note intervals) at specific times, places, and moods within a song.

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