# A Diminished 7th piano chord (Adim7) Adim7 contains A, C, E♭ and G♭. Three stacked minor thirds. E♭ and G♭ are black keys; A and C are white. - Canonical page: https://piano.org/chords/diminished-7th/a/ - Entity: chord:diminished-7th:a - Notes: A C E♭ G♭ - Formula: 1 ♭3 ♭5 ♭♭7 - Intervals from root: P1, m3, TT, M6 - Interval stack (semitones): 3 3 3 - Also written: Adim7, Adim7, A diminished 7th - Parameters: A440, 12-TET, 165 mm octave, spans centre to centre ## Construction | Degree | Note | Interval from root | Semitones | | --- | --- | --- | --- | | 1 | A | Perfect unison | 0 | | ♭3 | C | Minor third | 3 | | ♭5 | E♭ | Tritone | 6 | | ♭♭7 | G♭ | Major sixth | 9 | ## Fingering Rest your right hand over the notes with finger 1 on A, finger 2 on C, finger 3 on E♭, finger 5 on G♭. The left hand mirrors it. Right hand 1-2-3-5, left hand 5-3-2-1. Source: piano.org fingering method v1. ## Inversions | Position | Bass | Notes in order | Figured bass | Span | | --- | --- | --- | --- | --- | | Root position | A | A3 C4 E♭4 G♭4 | 7 | 9 st, 124 mm | | First inversion (Adim7/C) | C | C4 E♭4 G♭4 A4 | 6/5 | 9 st, 124 mm | | Second inversion (Adim7/E♭) | E♭ | E♭4 G♭4 A4 C5 | 4/3 | 9 st, 124 mm | | Third inversion (Adim7/G♭) | G♭ | G♭4 A4 C5 E♭5 | 4/2 | 9 st, 124 mm | ## Voicings (10) | Voicing | Notes | Span | Relation | Omits or adds | | --- | --- | --- | --- | --- | | Close, root position | A3 C4 E♭4 G♭4 | 9 st, 124 mm | identical | none | | Close, first inversion | C4 E♭4 G♭4 A4 | 9 st, 124 mm | identical | none | | Close, second inversion | E♭4 G♭4 A4 C5 | 9 st, 124 mm | identical | none | | Close, third inversion | G♭4 A4 C5 E♭5 | 9 st, 124 mm | identical | none | | Drop 2 | E♭3 A3 C4 G♭4 | 15 st, 206 mm | identical | none | | Drop 3 | C3 A3 E♭4 G♭4 | 18 st, 248 mm | identical | none | | Drop 2 and 4 | A2 E♭3 C4 G♭4 | 21 st, 289 mm | identical | none | | Shell, root ♭♭7 ♭3 | A2 G♭3 C4 | 15 st, 206 mm | subset | omits E♭ | | Guide tones, ♭3 and ♭♭7 | C4 G♭4 | 6 st, 83 mm | subset | omits A and E♭ | | Rootless close | C4 E♭4 G♭4 | 6 st, 83 mm | subset | omits A | ## One-edit neighbors | Becomes | Edit | Changes | Common tones | | --- | --- | --- | --- | | Adim | 1 ♭3 ♭5 | drops G♭ | 3 | | Am7♭5 | 1 ♭3 ♭5 ♭7 | G♭ becomes G | 3 | | Am6 | 1 ♭3 5 6 | E♭ becomes E | 3 | | Am | 1 ♭3 5 | E♭, G♭ becomes E | 2 | | Am7 | 1 ♭3 5 ♭7 | E♭, G♭ becomes E, G | 2 | | AmMaj7 | 1 ♭3 5 7 | E♭, G♭ becomes E, G♯ | 2 | | A6 | 1 3 5 6 | C, E♭ becomes C♯, E | 2 | ## Set theory - Absolute pitch classes: {9, 0, 3, 6} - Relative pitch classes: [0, 3, 6, 9] - Normal order: [0, 3, 6, 9] - Prime form: (0369) - Forte number: 4-28 - Interval vector: <004002> ## Frequencies (close root position) | Note | MIDI | Frequency | | --- | --- | --- | | A3 | 57 | 220.00 Hz | | C4 | 60 | 261.63 Hz | | E♭4 | 63 | 311.13 Hz | | G♭4 | 66 | 369.99 Hz | ## Questions and answers ### What notes are in Adim7? Adim7 contains A, C, E♭ and G♭. The formula is 1, ♭3, ♭5, ♭♭7. ### How do you play Adim7 on piano? Play A, C, E♭ and G♭ together. Right hand fingers 1, 2, 3, 5; left hand 5, 3, 2, 1. E♭ and G♭ are black keys; A and C are white. ### What are the inversions of Adim7? 4 positions: root position A C E♭ G♭, Adim7/C, Adim7/E♭, Adim7/G♭. ### What is the difference between Adim7 and Adim? Drops G♭. 3 of the notes are shared. ### What is an easy Adim7 for small hands? The guide tones, ♭3 and ♭♭7 voicing, C4 G♭4, spans 6 semitones or about 83 mm. ### What are the frequencies of Adim7? From A3 at A440 in 12-TET: 220.00, 261.63, 311.13, 369.99 Hz. ### What is the set class of Adim7? Prime form (0369), Forte 4-28, interval vector <004002>. ### How do I transpose Adim7 to another key? Keep the 1, ♭3, ♭5, ♭♭7 formula on the new root. C♯dim7 is C♯, E, G, B♭; Ddim7 is D, F, A♭, C♭. ## Provenance Every derived value above is computed by the piano.org theory kernel from the root, the quality and the stated parameters. Nothing is hand-entered per chord. Machine record: https://piano.org/api/knowledge/v1/entities/chord:diminished-7th:a Last reviewed: 2026-08-12