Find chords for a melody

Find a likely centre

Play or sing the melody and notice where it feels settled. Collect its notes, but do not decide the key from the first or last note alone. Try a possible tonic chord at the ending. If it feels like home, you have a working hypothesis to test against the rest.

Find the moments with harmonic weight

Start with one chord per bar or phrase. Long notes, accented notes and endings are useful anchors. If a melody holds E in C major, C, Am and Em are natural triads to try: all contain E. The following melody notes may make one choice more convincing.

A bar groups a number of beats; a phrase is a small musical statement that may span several bars. If you do not count bars yet, start where the melody holds a note or takes a natural pause.

Not every melody note must belong to the chord

E–F–G can sit over C. E and G are chord tones; F can pass between them. A long, accented F creates a different tension from a short F on a weak beat. Rhythm and resolution therefore matter as much as belonging to a scale.

This is the difference between a scale note and a chord tone. F belongs to C major but not to the C triad C–E–G. Being inside the scale does not mean being free of tension over this chord.

Listen to the progression, not only the moment

Try C–F–G–C, then replace the opening C with Am. Individually possible chords do not automatically make a satisfying progression. Listen to the bass line, repetition and direction towards a goal. I, IV and V make a useful start; vi and ii add more colours. Notes outside the scale can also be intentional.

Try it at the piano

Compare the three chords below with E4 on top. Then play E–F–G over C without changing chord for each note. Make F short and G long, then swap their lengths.