how to harmonize a melody
to harmonize a melody, find its key, mark where each phrase ends, and choose a chord for each beat or bar that contains the most important melody note there, ending phrases with a cadence such as V to I. then write a bass line under those chords and check the result by playing it. the method works the same on paper or in a notation editor, and it needs only the chords of one key to start.
- harmony is the chords under a tune; harmonizing is choosing them.
- every note of a major scale belongs to at least three of the key's chords, so there is always a choice.
- the strongest choices happen at the ends of phrases, which is why you plan the cadences first.
what chords fit a melody note?
a chord fits a melody note when that note is one of the chord's own notes. in C major, the note E belongs to C (C E G), Em (E G B) and Am (A C E), so all three can sit under it. the table lists each note of the scale and its chords.
| melody note | chords that contain it | in Roman numerals |
|---|---|---|
| C | C, Am, F | I, vi, IV |
| D | G, Dm, B° | V, ii, vii° |
| E | C, Em, Am | I, iii, vi |
| F | F, Dm, B°, and G7 | IV, ii, vii°, V7 |
| G | C, G, Em | I, V, iii |
| A | F, Am, Dm | IV, vi, ii |
| B | G, Em, B° | V, iii, vii° |
the same pattern holds in every major key once you swap the letter names, which is why harmony is usually taught in Roman numerals. our chord progression guide explains the numerals and what job each chord does.
harmonizing a melody, step by step
- find the key. look at the key signature and at the last note, which is usually the tonic. a tune in C major tends to end on C.
- mark the cadences. find where each phrase ends, often every four bars. plan V at the end of a phrase that should sound open, and V to I at the end of one that should sound finished.
- pick a harmonic rhythm. decide how often the chord changes: once a bar is a good default, twice a bar for a slow hymn-like tune.
- choose the chords. for each chord slot, look at the notes on the strong beats and pick a chord that contains them. notes on weak beats that don't fit are usually passing notes, and they can be left alone.
- prefer I, IV and V. they are the strongest chords in the key. use ii, iii and vi to vary a phrase that repeats.
- write the bass line. roots of the chords work, but a bass that moves by step, using inversions like C/E, sounds smoother.
- play it. listen for any chord that clashes with a held melody note, and for two chords in a row that sound the same.
a worked example: Ode to Joy in C major
the theme from Beethoven's ninth symphony is in the public domain and moves almost entirely by step, which makes it a good first melody. here are its first eight bars in C major in 4/4, with one chord a bar and a split bar at each cadence.
| bar | melody | chord | why |
|---|---|---|---|
| 1 | E E F G | C | E and G are in C; F is a passing note between them |
| 2 | G F E D | G7 | G, F and D are all in G7 |
| 3 | C C D E | C | C and E on the strong beats |
| 4 | E (dotted) D, D (half) | C, then G | a half cadence: the phrase stops on V and waits |
| 5 | E E F G | C | the opening comes back |
| 6 | G F E D | G7 | as in bar 2 |
| 7 | C C D E | C | as in bar 3 |
| 8 | D (dotted) C, C (half) | G, then C | an authentic cadence: V to I, the "finished" sound |
the only difference between the two phrases is the last bar, and the chords show it: the first phrase ends on G and sounds like a question, the second ends on C and sounds like the answer. once that works, try Am in bar 7 in place of C, and hear how the same melody note can change colour.
mistakes that make a harmonization sound wrong
- a clash on a long note. a melody note held for two beats or more has to belong to the chord under it.
- V after I at the very end. ending on V sounds unfinished. keep V to I for the last cadence.
- too many chords. changing on every note makes a simple tune sound busy. one or two chords a bar is plenty.
- parallel fifths and octaves. if you write the chords out in four parts, avoid two voices moving in parallel fifths or octaves, which thins the sound.
harmonizing in notei
notei is a music notation editor that runs in the browser. on every plan you can write the melody, put chord symbols above it, play it back with sampled instruments, and ask the built-in assistant why a chord works or what else could go there. the assistant's harmonise tool, which writes a harmony under your line as editable notes, is on notei+ and full score, not on the free plan. whichever way the chords arrive, play them back and keep only what you like.
common questions about harmonizing
what is the easiest way to harmonize a melody?
start with only three chords, I, IV and V, which are C, F and G in C major. put one chord under each bar, chosen so that it contains the melody notes on beats 1 and 3, and end with V to I. most folk tunes and many hymns can be harmonized with those three chords alone.
how many chords should go under each bar?
one chord per bar is a good default, and two per bar suits slower music. near a cadence the chords often change faster, as in bar 8 of the example above, where G moves to C halfway through the bar.
does every melody note have to be in the chord?
no. notes on strong beats and long notes should be in the chord. short notes between them, such as the F between E and G in Ode to Joy, are passing notes, and they sound fine against a chord that does not contain them.
can AI harmonize a melody for me?
yes, several tools can, including notei's harmonise tool on its paid plans. treat the result as a draft: play it back, check it against the steps above, and change any chord that doesn't sound right to you. you learn more by comparing its choices with your own.
do I need to know music theory to harmonize a tune?
only a little. you need to know the notes of the key and which notes make up its chords, which the table above lists for C major. the rest is listening, and an editor with playback lets you hear each choice straight away.
sources
- Open Music Theory: introduction to harmony
- Open Music Theory: Roman numerals
- Open Music Theory: chords in SATB style (doubling and spacing)
- Wikipedia: harmonization
this page is part of the how to write sheet music guide series. notei publishes it, and notei is our product. related: how to voice chords, how to write a walking bass line and the chord identifier.
written and checked by the notei team. how these guides are written and corrected.