How to Find Chords for a Melody You Already Have

To find chords for a melody, work out its key, then list the seven chords that belong to that key. For each bar, pick a chord that contains the melody’s most important note (the one on the first beat or the one held longest) and play the two together to check by ear. Start with the I, IV and V chords: between them they contain every note of the major scale, so every note in the key fits at least one of them.

Step 1: find the key of your melody

You need the melody as note names before you can choose chords, and you can get there without reading music. Record it on your phone, sung or hummed slowly. Play it back a phrase at a time and tap keys on a keyboard or piano app until one matches each pitch, writing the letters down as you go. Melodies mostly move in small steps, so the next note is usually one or two keys from the last.

With the notes written down, look for two things.

First, the home note. This is the tonic, the note the melody feels finished on. Most melodies end on it, and many keep circling back to it. Hold that note on the keyboard while you sing the last line. If the final note sounds settled over it, you have found home. If it sounds like a question, try the note you sing most often.

Second, the sharps and flats. Collect every black-key note the melody uses. Together with the home note, they point to the key:

Each row holds a major key and its relative minor, which share all seven notes. The home note decides between them: white keys with home on C is C major, and white keys with home on A is A minor. A minor-key tune may also sharpen the note just below home (G# in A minor, D# in E minor). That doesn’t change the key; the last section covers it.

Short melodies can be ambiguous. A tune built only from C, D, E, G and A (the C major pentatonic scale) has no F, F#, B or Bb in it, so it fits C major, G major and F major equally well. Trust the home note. If the tune ends on C and feels settled there, call it C major and move on.

Step 2: match chords to the long notes

Every major key has seven chords built only from its own notes, which theory calls the diatonic chords. In C major they are C, Dm, Em, F, G, Am and Bdim, numbered I ii iii IV V vi vii°. The same pattern builds the chords in any key, and how to find the chords in any key walks through it.

Each note of the scale sits inside three of those chords, so any melody note in the key gives you exactly three candidates:

Now go through the melody bar by bar:

1. Find the notes that matter. Those are the note on the first beat of the bar and the note held longest. Quick notes between them are passing notes, and they don’t need to be in the chord.
2. Pick a chord that contains them. If one chord holds both important notes, use it for the whole bar. If none does, split the bar and give each half its own chord.
3. Start and end on I. The first and last chord of a song or section is usually the home chord.
4. Put V right before the end. G going to C at the end of a phrase is the strongest landing in C major.
5. Try I, IV and V first. Then swap in vi, ii or iii wherever a bar sounds too plain.

Here is the method on Twinkle, Twinkle, Little Star in C, a tune nearly everyone can hum. The opening phrase is C C G G, A A G, F F E E, D D C: four bars of 4/4, with the last note of bars 2 and 4 held for two beats.

In both columns, each chord contains the note it sits under, so both are correct. The plain column uses only I, IV and V and sounds like the nursery rhyme you remember. The moodier column swaps in Em, Am and Dm (iii, vi and ii), which makes half its chords minor, and played slowly the same tune turns wistful.

How to know what chords go with a melody by ear

The table narrows each note to three chords. These checks help your ears pick one.

Start with roots only. Before full chords, play just the bottom note of each chord (C, F, G or A for I, IV, V and vi) as a single low note under the melody. Judging one bass note against a tune is easier than judging a whole chord, and you can do it with one finger while you sing.

Then listen for the half-step rub. The clash to catch is a held melody note one half step above a note in the chord. Sing a long F over a C chord and the F grinds against the chord’s E. You don’t always need a new chord for that: change C to Csus4 (C F G) and the F becomes part of the chord, then go back to C when the melody drops to E. A D held over C (making Cadd9) or an A over C (making C6) sounds fine, because neither sits a half step above a chord note.

Last, cycle the candidates. Loop one bar of the melody and try each chord that contains its main note. Often one sounds obvious and another sounds more interesting. Use the obvious one in the first verse and save the other for later in the song.

A chord player makes this faster than fumbling guitar shapes. The free online chord player plays the chords of all 24 keys from pads, so you can sing over them in the key you found in step 1. Our iPhone app Gelato Chord puts the seven chords of your key on seven keys, and its melody plate lights up the strings in the chord you are holding, so you can see whether your melody note is in it. All of that is in the free Play mode.

How to find chords for a vocal melody

Vocal melodies are harder to pin down than played ones, because voices slide: a singer scoops up into a note or sags a little on a long vowel. Sing slower than you would perform it and hold the long notes. When you match notes, go for the pitch the voice settles on, usually in the middle of the syllable, and ignore the slide into it.

Find the last note of the tune first and keep it sounding while you work, on a held key or hummed. It is usually the home note, and each other note is easier to place once you hear it against home.

If single notes are going nowhere, work the other way round. Guess the key from the last note and loop its I, IV, V and vi chords while you sing (for a tune ending on G: G, C, D and Em). If the melody sits comfortably over them, the guess is right. If every chord sounds slightly off, move the whole set up or down a half step and try again.

Our other app, Gelato Synth, helps with the note-finding part: in Notes mode the pads play only the notes of the root and scale you pick, so once you have a guess at the key, every pad is a candidate for the next sung note. Its Chords mode (part of the one-time $4.99 purchase) turns the same screen into the chords of that key, labeled with Roman numerals.

When the right chord isn’t in the key

Sometimes a melody uses a note from outside the key, and none of the seven chords holds it. In C major that could be a Bb, an Ab, an F# or a G#. Treat the odd note as a clue, because it usually points at the chord you need.

Bb and Fm are borrowed chords, taken from C minor, the key with the same home note. Fm is the one to know. Play F, Fm, C under a melody that slips from A to Ab to G, and each melody note sits in its chord while the line sinks by half steps into the home chord. It sounds bittersweet.

C7, D and E work differently. Each is the V chord of the chord it leads to: C7 pulls toward F, D toward G and E toward Am, the same way G pulls toward C. So an F# or a G# in a C major melody usually means the tune is heading for G or Am.

Minor keys have one of these built in. In A minor, a melody often raises G to G# on its way back up to A, and when it does, the V chord becomes E major (E G# B) in place of Em. E going to Am is the standard way to end a phrase in A minor.

Not every outside note needs a new chord. A quick F# on a weak beat between two Gs (G F# G) is decoration, so keep the chord you had under it. Change the chord when the odd note lands on the first beat of a bar or is held.