Path
What to study before Diminished chords
Minor thirds stacked until the chord is symmetrical, and has no definite root. Below, the concepts that come before, in the order in which one explains the next. Signed in, you see the same path minus what you already hold: your path.
Notes and semitones
The seven letter names, the accidentals that alter them, and the semitone as the system's smallest step.
Intervals
The distance between two notes, measured by a number taken from the letter names and a quality taken from the semitones.
Triads
Three-note chords stacked in thirds, and the four qualities that result.
Seventh chords
The fourth note stacked on the triad, and the five qualities the repertoire actually uses.
Major scale
Seven degrees built on a fixed sequence of tones and semitones, and the reference everything else is measured against.
Diatonic harmony
The chords that arise from stacking thirds on each degree of a scale, and why each quality lands where it does.
Harmonic function
The role each degree plays — tonic, subdominant, or dominant — and the tension that moves one to the next.
Diminished chords
Minor thirds stacked until the chord is symmetrical, and has no definite root.