What Is a Chord in Music? Notes, Triads, and Harmony

If you play several different notes at roughly the same time, they can form a chord. In many Western music traditions, one common starting point is the triad, a three-note chord built from a root, a third, and a fifth. The root gives the chord its basic name.

For example, a C major triad contains C, E, and G. C is the root. The distances from C to E and from E to G help produce the major quality. A C minor triad changes E to E flat, altering the interval pattern and giving the chord a different sound.

This triad example explains chords at a beginner level, but chords can contain more than three notes. Seventh chords add another chord tone, and musicians can extend or alter chords in many ways. The key idea is that the notes work together as a harmonic shape.

A chord does not always place its root at the bottom. If C, E, and G are rearranged so E or G is the lowest note, the chord can still function as a C major triad. These rearrangements are called inversions.

Inversions change the spacing and bass note, which can make a progression sound smoother or give a particular line more movement. Musicians also spread chord tones across several octaves, double notes, or leave some notes out depending on the instrument and style.

That flexibility matters when learning about chords. You do not identify every chord only by the exact lowest-to-highest order of notes. You look for the underlying set of chord tones and consider the musical context.

Chords can do several jobs at once:

• •Support a melody by giving its notes a harmonic setting.
• •Create a sense of stability or tension depending on the chord and context.
• •Form progressions that give a section direction over time.
• •Change colour through major, minor, seventh, suspended, and other chord types.
• •Shape the bass line through root position and inversions.

Chords also gain meaning from what comes before and after them. A major triad can sound settled in one key and surprisingly unstable in another context. Musicians describe chord function to explain these relationships, such as a dominant harmony creating a strong pull toward a tonic. This is another layer of a chord in music: a chord has its own notes, but its role becomes clearer when you hear it as part of a progression.

The easiest way to hear what a chord in music is is to alternate between single notes and stacked notes. Play a melody note alone, then add two supporting notes beneath it. Listen for the change from a single pitch line to a fuller harmonic sound. Your ear can learn the concept before you memorise every chord symbol.

A useful exercise is to build a triad on every note of a major scale, using only notes from that scale. In C major, start on each note and stack two more by skipping a letter each time: C-E-G, D-F-A, E-G-B, F-A-C, G-B-D, A-C-E and B-D-F. Three of these are major chords, built on the first, fourth and fifth notes. Three are minor, built on the second, third and sixth notes. The chord on the seventh note is diminished. Musicians label them with Roman numerals, using capitals for major and lower case for minor: I, ii, iii, IV, V, vi and a diminished vii.

These numbers reveal patterns shared by thousands of songs. The progression I, IV, V, using C, F and G in C major, underpins much blues, folk and early rock and roll. Another very common pop pattern runs I, V, vi, IV, which in C major is C, G, A minor, F. Because Roman numerals describe positions in the key rather than particular notes, you can move a progression to any key. In G major, the same I, V, vi, IV pattern becomes G, D, E minor, C. Learning to hear these shapes lets you work out many songs by ear far more quickly.

In pop, jazz and folk music, chords are usually written as short symbols above the melody or lyrics, and each symbol is a compact recipe. A letter on its own, such as C, means a major triad, C, E and G. A small m makes it minor, so Cm is C, E flat and G. Adding 7 means a minor seventh above the root, so C7 is C, E, G and B flat, while Cmaj7 uses B natural instead. Csus4 replaces the third with the fourth, giving C, F and G, and a slash chord such as C/E tells you to put E in the bass.

The plain 7 chord deserves special attention because it is built to move. In C major, the chord on the fifth note is G7: G, B, D and F. B and F are a tritone apart, an interval of three whole tones that sounds restless. When the chord resolves to C, the B usually rises a semitone to C and the F falls a semitone to E, so the tension collapses into two notes of the home chord. That is why a dominant seventh can make a listener expect the next chord almost before it is played, and why it appears at so many endings.

A note played on a real instrument contains not just one frequency but a series of overtones, called harmonics, at whole-number multiples of the lowest one. Play a low C and listen carefully, and the fourth, fifth and sixth harmonics are C, E and G: a major triad hidden inside a single note. In frequency, a pure major triad sits in the ratio 4 to 5 to 6. Start from A at 440 hertz and the pure major third above it is 550 hertz, with the fifth at 660. Because these simple ratios share many overtones, the notes reinforce each other rather than clash.

Modern keyboards, however, do not use those pure ratios. Equal temperament divides the octave into twelve identical semitones so that music can move freely between keys, and the price is that most intervals are slightly out of tune. The fifth is almost perfect, only about one fiftieth of a semitone narrow. The major third is about one seventh of a semitone wide, so the C sharp above A 440 sits at about 554 hertz instead of 550. Barbershop quartets and string players often tune their thirds lower by ear, which is one reason their major chords can sound unusually smooth and ringing.

A chord is a collection of notes treated as one harmonic unit, often built around a root. Start with major and minor triads, learn how inversions rearrange the same notes, and listen for how chords move from tension toward rest. Once you connect the written notes with the sound they create together, harmony becomes far less abstract.