C Added 9th Chord

Chord Tones: C Added 9th Chord

Symbol: add9, add2 — Formula: 1-3-5-9

Chord Notation

Roman numeral (e.g. I, IV, V) and Nashville Number notation are key-dependent. See Keys pages for chord function within specific keys.

Inversions

Harmonic Function

The C add9 chord commonly functions as the tonic (I) in C major/minor. Its harmonic role varies by key — in major keys it provides stable harmonic grounding.

The add9 chord adds a ninth (octave + second) to a major triad without including the seventh. It has a bright, open sound, richer than a plain major chord but less complex than a major ninth. The C Added 9th Chord specifically contains 4 notes: C, E, G, D (formula: 1-3-5-9). On piano, C-rooted chords sit entirely on white keys in their basic triad form, making them the first chords most students learn. Pop, folk, and singer-songwriter music heavily use C-rooted chords because open-position guitar voicings and piano shapes are immediately accessible.

Common Progressions

The C Added 9th Chord frequently appears in these progression patterns (shown in Roman numeral notation relative to key):

• Iadd9-IVadd9
• Iadd9-V

Songs Featuring the Added 9th Chord

Well-known songs where the C Added 9th Chord — or this chord type — plays a prominent role:

• Every Breath You Take – The Police
• With or Without You – U2
• Right Here Waiting – Richard Marx

Tuning Frequencies Across Temperaments

Frequencies shown at A=440 Hz. View full temperament data for any note.

Scales Containing the C Added 9th Chord

These scales include the C Added 9th Chord as a diatonic or characteristic chord: