To harmonize a melody you’ve already written, work out the key, look at which melody notes land on the strong beats, and pick chords from that key that contain those notes. Then string those candidate chords into a progression that sounds right and test the whole thing by ear. That’s the entire job. Everything below is just how to do each step without a theory degree. (This assumes you already have the tune. If you don’t yet, write one first with how to write a melody for your lyrics.)
This is the companion to figuring out how to add chords to lyrics. There the assumption is you already know the chords and need to write them down. Here you have a tune in your head or under your fingers, and you’re hunting for the chords that belong underneath it. Whether you spell it harmonize or harmonize, the process is the same.
How do I find the key of my melody?
Start by finding the note the melody feels finished on. Hum your tune to the end and hold the last note. Nine times out of ten, that resting note is the root of your key. If your melody settles on C and feels at home there, you’re probably in C major.
A quick confirmation: play a C major chord under that final note and see if it sounds like an arrival. If it does, you’re in C. If the tune feels sadder and lands on A instead, you might be in A minor, which shares all the same notes.
Once you know the key, you know your chord pool. In C major the seven chords are C, Dm, Em, F, G, Am, and Bdim. In practice you’ll only reach for C, F, G, Am, and Dm most of the time. Those five cover most folk, pop, and singer-songwriter material.
If you don’t read music and can’t name the notes yet, that’s fine. You can still harmonize entirely by ear using the steps below. Naming things just makes it faster.
Which melody notes actually need a chord?
Not every note matters equally. Chords are chosen to fit the melody notes on the strong beats, not the quick passing notes in between. In 4/4 time the strong beats are 1 and 3, with beat 1 doing the most work.
Sing your melody slowly and tap your foot. The notes that land on your downbeats are the ones a chord has to agree with. The little runs and pickups that scurry between them can clash slightly and nobody will mind, because the ear latches onto what happens on the beat.
Take the opening of “Twinkle Twinkle Little Star,” which is public domain. In C, the melody starts C C G G A A G. The first strong note is C, the next strong resting point is G. If you get a chord to fit C at the start and a chord to fit G a bar later, the fast notes take care of themselves.
So before you touch a single chord, mark your strong-beat notes. Those are your targets.
How do I pick a chord that fits a note?
A chord fits a melody note when that note is one of the chord’s three notes. That’s the whole rule. A C major chord is C, E, and G, so it comfortably supports a melody sitting on any of those.
Here’s the useful part: every note in the key belongs to more than one chord. If your strong beat is an E, three chords in C contain an E:
- C major (C E G)
- Em (E G B)
- Am (A C E)
All three will “work.” They just feel different. C sounds bright and settled, Am sounds wistful, Em sits somewhere in between. This is where harmonizing stops being math and starts being a choice.
My advice: for each strong-beat note, jot down the two or three chords in the key that contain it. Don’t decide yet. You’re building a menu of legal options for each moment, and you’ll choose between them in the next step based on how they flow.
One caution. When you’re stuck on a note, the I chord (C in the key of C) and the V chord (G) fit an enormous number of melody notes between them, so leaning on those two is a safe way to get a rough harmonization down fast. Just don’t let the whole song become two chords out of laziness.
Should I start from common progressions instead of note by note?
Often, yes. Going note by note is thorough but slow, and it can produce a lurching, over-harmonized result where the chord changes on every syllable. A faster route is to audition a familiar progression and let your melody sit on top of it.
Try the workhorses in your key and see which one your tune already agrees with:
- I to V to vi to IV (C, G, Am, F) for a bright modern pop feel
- I to IV to V (C, F, G) for folk, blues, and country
- vi to IV to I to V (Am, F, C, G) for something more melancholic
Loop one of these under your melody and listen for the moments where the melody note fights the chord. Usually you’ll find that most of the tune fits, and only a bar or two needs a swap. That’s a much easier problem than harmonizing from a blank page. If you want the full tour of these loops and the moods they carry, I wrote up the common chord progressions for songwriters separately.
Thinking in Roman numerals (I, IV, V) rather than fixed chord names also lets you move a working harmonization into any key your voice prefers. That number-based approach is the heart of the Nashville Number System, and it’s worth learning early.
How do I test whether the harmony works?
You test by ear, out loud, with the melody and the chord together. A harmony is right when the melody note on the beat sits inside the chord and the change to the next chord feels earned rather than random. Reading it on paper is not the same as hearing it.
Play a candidate chord and sing the strong-beat note over it. Two things to listen for:
- Does the note belong? If it rings clean and stable, the chord contains it. If it grinds or sounds sour on the downbeat, that chord doesn’t fit and you should try another from your menu.
- Does the move feel good? Play the chord before it and the chord after it. Harmony is about motion, so a chord that fits in isolation can still feel wrong in the sequence. Trust that reaction and swap it.
When two chords both fit and both sound fine, pick the one that supports the emotion of the line. A hopeful lyric wants the major (C); a heavier line often wants its relative minor (Am). The melody tells you what fits; the words tell you which of the fits to choose.
Work one phrase at a time. Lock the chords under your first line before moving on, then reharmonize the second line and check that the join between them lands. Small, verified steps beat one big guess every time.
A quick worked example
Say your melody, in C, holds a long E on beat 1 of the first bar, then a long G on beat 1 of the second. Your menu for E is C, Em, or Am. Your menu for G is C, Em, or G. Pick C for the first bar (bright, settled) and G for the second (it fits the G and pulls forward), and you’ve harmonized two bars in under a minute. Sing it back. If the G bar feels too restless, try Em instead and hear the difference. That back and forth is the craft.
When you’ve found chords you like, the next job is pinning each one over the exact word it belongs to so the harmony survives your next round of lyric edits. Songwriter Studio anchors each chord to the exact syllable and keeps it there through later edits, which turns “I think this is an Am” into something written down rather than remembered. If you write on iPhone or iPad, you can try it on the App Store or see how the chord tools fit the rest of the writing features.
Related: Once you have chords, learn to notate them cleanly with how to add chords to lyrics, pick stronger loops from common chord progressions for songwriters, and make your harmonies key-independent with the Nashville Number System.
