# C♯ Diminished 7th piano chord (C♯dim7) C♯dim7 contains C♯, E, G and B♭. Three stacked minor thirds. C♯ and B♭ are black keys; E and G are white. - Canonical page: https://piano.org/chords/diminished-7th/c-sharp/ - Entity: chord:diminished-7th:c-sharp - Notes: C♯ E G B♭ - Formula: 1 ♭3 ♭5 ♭♭7 - Intervals from root: P1, m3, TT, M6 - Interval stack (semitones): 3 3 3 - Also written: C♯dim7, C#dim7, C♯ diminished 7th - Parameters: A440, 12-TET, 165 mm octave, spans centre to centre ## Construction | Degree | Note | Interval from root | Semitones | | --- | --- | --- | --- | | 1 | C♯ | Perfect unison | 0 | | ♭3 | E | Minor third | 3 | | ♭5 | G | Tritone | 6 | | ♭♭7 | B♭ | Major sixth | 9 | ## Fingering Rest your right hand over the notes with finger 2 on C♯, finger 3 on E, finger 4 on G, finger 5 on B♭. The left hand mirrors it. Right hand 2-3-4-5, left hand 5-4-3-2. Source: piano.org fingering method v1. ## Inversions | Position | Bass | Notes in order | Figured bass | Span | | --- | --- | --- | --- | --- | | Root position | C♯ | C♯3 E3 G3 B♭3 | 7 | 9 st, 124 mm | | First inversion (C♯dim7/E) | E | E3 G3 B♭3 C♯4 | 6/5 | 9 st, 124 mm | | Second inversion (C♯dim7/G) | G | G3 B♭3 C♯4 E4 | 4/3 | 9 st, 124 mm | | Third inversion (C♯dim7/B♭) | B♭ | B♭3 C♯4 E4 G4 | 4/2 | 9 st, 124 mm | ## Voicings (10) | Voicing | Notes | Span | Relation | Omits or adds | | --- | --- | --- | --- | --- | | Close, root position | C♯3 E3 G3 B♭3 | 9 st, 124 mm | identical | none | | Close, first inversion | E3 G3 B♭3 C♯4 | 9 st, 124 mm | identical | none | | Close, second inversion | G3 B♭3 C♯4 E4 | 9 st, 124 mm | identical | none | | Close, third inversion | B♭3 C♯4 E4 G4 | 9 st, 124 mm | identical | none | | Drop 2 | G2 C♯3 E3 B♭3 | 15 st, 206 mm | identical | none | | Drop 3 | E2 C♯3 G3 B♭3 | 18 st, 248 mm | identical | none | | Drop 2 and 4 | C♯2 G2 E3 B♭3 | 21 st, 289 mm | identical | none | | Shell, root ♭♭7 ♭3 | C♯2 B♭2 E3 | 15 st, 206 mm | subset | omits G | | Guide tones, ♭3 and ♭♭7 | E3 B♭3 | 6 st, 83 mm | subset | omits C♯ and G | | Rootless close | E3 G3 B♭3 | 6 st, 83 mm | subset | omits C♯ | ## One-edit neighbors | Becomes | Edit | Changes | Common tones | | --- | --- | --- | --- | | C♯dim | 1 ♭3 ♭5 | drops B♭ | 3 | | C♯m7♭5 | 1 ♭3 ♭5 ♭7 | B♭ becomes B | 3 | | C♯m6 | 1 ♭3 5 6 | G becomes G♯ | 3 | | C♯m | 1 ♭3 5 | G, B♭ becomes G♯ | 2 | | C♯m7 | 1 ♭3 5 ♭7 | G, B♭ becomes G♯, B | 2 | | C♯mMaj7 | 1 ♭3 5 7 | G, B♭ becomes G♯, B♯ | 2 | | C♯6 | 1 3 5 6 | E, G becomes E♯, G♯ | 2 | ## Set theory - Absolute pitch classes: {1, 4, 7, 10} - Relative pitch classes: [0, 3, 6, 9] - Normal order: [1, 4, 7, 10] - Prime form: (0369) - Forte number: 4-28 - Interval vector: <004002> ## Frequencies (close root position) | Note | MIDI | Frequency | | --- | --- | --- | | C♯3 | 49 | 138.59 Hz | | E3 | 52 | 164.81 Hz | | G3 | 55 | 196.00 Hz | | B♭3 | 58 | 233.08 Hz | ## Questions and answers ### What notes are in C♯dim7? C♯dim7 contains C♯, E, G and B♭. The formula is 1, ♭3, ♭5, ♭♭7. ### How do you play C♯dim7 on piano? Play C♯, E, G and B♭ together. Right hand fingers 2, 3, 4, 5; left hand 5, 4, 3, 2. C♯ and B♭ are black keys; E and G are white. ### What are the inversions of C♯dim7? 4 positions: root position C♯ E G B♭, C♯dim7/E, C♯dim7/G, C♯dim7/B♭. ### What is the difference between C♯dim7 and C♯dim? Drops B♭. 3 of the notes are shared. ### What is an easy C♯dim7 for small hands? The guide tones, ♭3 and ♭♭7 voicing, E3 B♭3, spans 6 semitones or about 83 mm. ### What are the frequencies of C♯dim7? From C♯3 at A440 in 12-TET: 138.59, 164.81, 196.00, 233.08 Hz. ### What is the set class of C♯dim7? Prime form (0369), Forte 4-28, interval vector <004002>. ### How do I transpose C♯dim7 to another key? Keep the 1, ♭3, ♭5, ♭♭7 formula on the new root. Ddim7 is D, F, A♭, C♭; D♯dim7 is D♯, F♯, A, C. ### Is D♭dim7 the same as C♯dim7? Enharmonically yes: the same piano keys and the same sound, spelled differently. ## 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:c-sharp Last reviewed: 2026-08-12