How do notes form a chord together?

Several notes sounded together can form one recognizable harmonic group. A chord describes such a group, and a triad is a three-note chord built from a root, a third and a fifth in its basic arrangement. The relationships between pitches help distinguish the chord even when the whole group moves higher or lower.

The C major triad contains C4, E4 and G4. From its root C, E is four semitone steps higher, a major third, and G is seven semitones higher, a perfect fifth. A semitone is one step in the usual twelve-step octave division. In the pictured block chord, all three notes begin together and last two beats.

C minor keeps C and G but lowers E to E-flat. Its root-to-third span is now three semitones instead of four. A small change in one note changes the interval relationship and therefore the chord quality. G major uses different notes—G3, B3 and D4—but preserves the major-third and perfect-fifth relationships above its root.

Major and minor name musical structures, not universal emotional scores. Context, listeners and musical traditions affect their expressive use. Chords can also have different voicings, with notes placed in different octaves, or be unfolded across time. The simultaneous example isolates one idea: changing a root can preserve a relationship, while changing an interval can alter the kind of chord.