Harmony is what happens when two or more notes sound at the same time, and how those combinations fit together and move through a piece. It is the vertical, stacked dimension of music: the layer sitting under the tune you actually hum. This is the overview. How harmony differs from melody and rhythm, what makes notes sound restful or tense together, and how a key, its chords and a progression build the harmony beneath a whole song.
Real theory, explained plainly. It works the same on a piano, a guitar, or in a piano roll, in any key and any style. Nothing here needs a particular instrument.
Harmony is two or more notes sounding at the same time, and the way those combinations fit together and change as a piece goes on. Where a single melody is one note after another, harmony is notes stacked on top of each other at the same moment.
It is the vertical dimension of music. Picture notes written on a page: melody reads left to right, one note following the next, while harmony reads up and down, several notes sounding together in the same instant. When someone says a song has rich harmony, or is just three chords, this stacked, sounded-together layer is what they mean.
The basic unit of harmony is the chord, a small group of notes sounded together. When chords change one after another you get a chord progression, which is simply harmony moving through time. Both of those have guides of their own; this one stays at the overview and looks at how the whole layer fits together, rather than working out each chord note by note.
Melody is the single line of notes you hum, one after another; harmony is the notes underneath it, sounding together at the same time. Melody is horizontal and one note at a time, harmony is vertical and several notes at once. They are two dimensions of the same music, not two separate pieces.
A third dimension, rhythm, is the timing of it all: when each note starts and how long it lasts, without saying which notes those are. Most music runs all three at once, a melody on top, harmony underneath it, and rhythm deciding when each part moves.
| Layer | What it is | How you notice it |
|---|---|---|
| Melody | One line of single notes, played in turn | The part you hum or whistle |
| Harmony | Notes sounded together, and how they change | The chords behind the tune, the mood underneath |
| Rhythm | The timing of the notes, long and short | The part you tap your foot to |
Melody and harmony lean on each other. The tune sits on top of the harmony, and the notes of a melody usually belong to the chord sounding under them at that moment, which is why a melody and its chords sound like they agree rather than fight. Change the chord underneath a held melody note and the very same note can turn sweet or sour; the harmony underneath is doing that.
Consonance is notes that sound stable and restful together; dissonance is notes that sound tense and unsettled, as if they want to move on to something calmer. Both describe how a combination of notes strikes the ear when it sounds.
A consonant combination feels at rest and finished, like a place you could stop. A dissonant one feels like it is leaning, holding tension that wants to release. Dissonance is not a mistake or a wrong note; it is tension you add on purpose and then resolve, and without it music would have nothing to let go of.
Music breathes by moving between the two. A passage that stayed perfectly consonant would sit still and go flat; one that stayed dissonant would wear the ear out. The pull from tension back to rest, dissonance resolving onto consonance, is a large part of what gives harmony its sense of motion and arrival.
How consonant or dissonant a combination sounds is partly a matter of style, context and habit, and where writers have drawn the line has shifted over the centuries. But the broad feeling of restful against tense is something most listeners hear straight away, and it is enough to write with.
You choose a key, build chords from it, and move between those chords under your melody, using the swing from tension to rest to give the song its shape. In practice that means picking a home, leaning away from it, and coming back.
A key, or the scale behind it, is the pool of notes harmony usually draws from. Choosing a key hands you a home note and a set of notes that belong together, and the chords built from those notes are the ones that sound settled in that key. Staying mostly inside the pool is what makes a song hold together; stepping outside it now and then is where surprise and colour come from.
From there, harmony is chords changing over time. You set a home chord, move away from it and return, which is exactly what a chord progression does, while the melody rides on top with its notes mostly taken from whatever chord is sounding underneath.
That is the shape of it, and this guide stays at the overview on purpose. For how a single chord is actually built, note by note, see what is a chord. For how to put chords in an order that leaves home and comes back, see how to write a chord progression. Those two ideas, one chord and then chords in motion, are what the whole of harmony is built from.
We built ARGISH to make harmony quick to hear. It is a self-playing chord synth: set a key and it generates chords and whole progressions that stay in that key, so you can hear harmony move under a melody instead of working it out on paper. It is an easy way to hear how notes sit together and change, which is the whole subject of this guide.
It runs free in your browser to try, and installs as AU, VST3, AAX or a standalone app when you want it inside your own sessions.
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