Harmony

Harmony is the study of chords — how they function, how they relate to each other, and how they’re used to add richness and emotion to music. When you add chords to a melody, you’re creating harmony: extra layers of sound that give a song depth and movement.

In popular music, harmony is built around a few core ideas: how chords establish a tonal center (the key), how they work in progressions, and how they create tension and release. A strong understanding of harmony helps you write music that feels grounded, emotionally resonant, and familiar — even when it’s new.

One of the most helpful things harmony explains is why certain chord combinations sound natural — and why some chords are used much more often than others. For example, in songs written in C major, some chords appear far more frequently than others. The chart below shows a breakdown of the most common chords in this key:

We can see that in C major, the chords C, F, G, and Am are the most common. These chords — I, IV, V, and vi — are the basic chords built from the C major scale.

But harmony doesn’t just explain which chords are likely to appear — it also helps predict where they’re likely to go. For example, in Hooktheory’s TheoryTab database, the data shows that for songs in C Major, after Em chords, the next chord is almost always F or Am.

Students familiar with harmony will recognize this as a natural progression. In the key of C major, Em is the iii chord — and one of its common tendencies is to move to the IV (F) or the vi (Am) chord.

You can explore patterns in harmony by visiting the Hooktheory Trends page, where you can see which chords are commonly used together and how likely one chord is to follow another — all backed by real examples from the TheoryTab database.