The diminished 7th stacks three minor 3rds (1–♭3–♭5–♭♭7). Fully symmetrical, it is the ultimate tension chord and a powerful passing/leading harmony.
NotesE · G · A♯ · C♯
Formula1 · ♭3 · ♭5 · ♭♭7
Every diminished 7th chord tone across the neck. Solo with these and you spell the chord — that's the difference between running a scale and playing the changes.
