Diminished Triad vs Diminished 7
The C diminished triad and the C diminished 7 share 3 notes — C, Eb, Gb. From there, the C diminished 7 adds Bbb.
Piano, C3 to C5. Notes in this scale, low to high: C3 (root of C Diminished Triad and root of C Diminished 7), Eb3 (flat 3 of C Diminished Triad and flat 3 of C Diminished 7), Gb3 (flat 5 of C Diminished Triad and flat 5 of C Diminished 7), Bbb3 (double flat 7), C4 (root of C Diminished Triad and root of C Diminished 7), Eb4 (flat 3 of C Diminished Triad and flat 3 of C Diminished 7), Gb4 (flat 5 of C Diminished Triad and flat 5 of C Diminished 7), Bbb4 (double flat 7), C5 (root of C Diminished Triad and root of C Diminished 7).
Both scales above are drawn on one piano keyboard in the key of C. Notes belonging to both are drawn as a split two-color dot, so the notes they share and the notes unique to each are visible in one picture.
How the formulas differ
Scale degrees are the key-independent way to compare two scales — these stay the same in every key, and they are what actually distinguishes one scale from another.
| Scale | Degrees |
|---|---|
| Diminished Triad | R · b3 · b5 |
| Diminished 7 | R · b3 · b5 · bb7 |
Notes in common
| Note | In Diminished Triad | In Diminished 7 |
|---|---|---|
| C | R | R |
| Eb | b3 | b3 |
| Gb | b5 | b5 |
Notes that differ
- Only in the diminished 7: Bbb (bb7)