chord

A C major chord. A chord is the simultaneous sound of two or more musical notes. The most common chord has three notes and is known as a triad. Added tone chords, extended chords, and tone clusters can have more than three notes and are common in contemporary classical music and jazz.

An arpeggio is a chord where notes are sounded separately. A series of chords is sometimes called a chord progression. There are several ways to notate chords including figured bass, Roman numerals, the Nashville Number System, and alphabetical chord notation.