sus2

Sus2, short for suspended second, is a triad in which the third of a major or minor triad is replaced by the second scale degree. The chord consists of the root, the second, and the fifth, giving a 1-2-5 pitch class structure. For example, in the key of C, Csus2 contains C, D, and G. Because the third is omitted, the chord lacks a defined major or minor quality, producing a suspended, open sound.

In practice, sus2 chords are often voiced in various inversions. The root may not be in the bass, but the chord is still identified by the suspended second relative to the root. Common voicings place the root, second, and fifth in different octaves to fit a bass line or texture, especially on piano and guitar.

Resolution and function: Sus2 typically resolves by moving the suspended second up to the third, yielding a major or minor triad. In C, Csus2 often resolves to C major (C-E-G) or sometimes to C minor (C-Eb-G) depending on the musical context. Voice-leading generally preserves smooth, stepwise motion, with the D moving to E and the remaining chord tones staying close. Sus4 chords (replacing the third with a fourth) follow a similar principle, and both are common as color or passing chords.

Usage: Sus2 chords are widely used in pop, rock, folk, and jazz as color chords or passing harmonies. They can substitute for the tonic triad in progressions or precede a resolution to a major or minor harmony.

Notation: Chords are written as Csus2, Dsus2, and so on. They are distinct from add9 chords, which include the third and a ninth rather than replacing the third.