Five infographics, each answering one question: what a note is, how far apart two notes are, how a scale is built, how a chord is built, and how keys relate to each other.
Twelve pitches repeat in every octave: seven natural notes (A–G) and five sharps/flats sitting between most of them. The gaps between B–C and E–F are naturally a half step, no black key needed.
An interval is the distance between two notes, counted in half steps (semitones). Every scale and chord is just a recipe of intervals stacked on a root note.
The major scale is a fixed pattern of whole (W) and half (H) steps: W‑W‑H‑W‑W‑W‑H. Start on any note and the pattern gives you that note's major scale.
Stack the 1st, 3rd, and 5th notes of a scale and you get a triad. A major 3rd (4 semitones) makes it sound major; a minor 3rd (3 semitones) makes it sound minor.
Moving clockwise, each key adds one sharp; moving counter‑clockwise, each key adds one flat. Neighbouring keys on the wheel share almost all their notes, which is why chord progressions love to move between them. It's also a shortcut to relative minors — the minor key sharing a key signature with each major.
Each note of a scale has a functional name independent of key — this vocabulary is used constantly in chord and scale discussion.
| Degree | Name | In C major |
|---|---|---|
| 1 | Tonic | C |
| 2 | Supertonic | D |
| 3 | Mediant | E |
| 4 | Subdominant | F |
| 5 | Dominant | G |
| 6 | Submediant | A |
| 7 | Leading tone | B |
Build a triad on each note of a scale using only notes from that scale, and you get the seven chords that "belong" to the key. Songs mostly draw from this set — which is why they sound coherent.
| Numeral | Quality | In C major | In G major | Role |
|---|---|---|---|---|
| I | major | C | G | home / rest |
| ii | minor | Dm | Am | pre-dominant |
| iii | minor | Em | Bm | colour, links I and vi |
| IV | major | F | C | movement away from home |
| V | major | G | D | tension, wants to resolve to I |
| vi | minor | Am | Em | the "relative minor," sadder home |
| vii° | diminished | B° | F#° | strong pull back to I (used rarely) |
The pattern of qualities is always major-minor-minor-major-major-minor-diminished for any major key. Learn it once and you know the chords of every key. The key tool spells them out for any root.
Most chord movement is about tension and release. The V chord contains the leading tone — the 7th degree, just a half step below the tonic — which creates a strong pull back home to I. That single resolution is the engine behind most Western music.
V → I is the strongest resolution. IV → I is gentler (the "amen" or plagal cadence). ii → V → I is the most common movement in jazz and pop because it builds tension in two stages before releasing.
Songs create interest by occasionally using a chord from outside the key — a "borrowed" chord — or a dominant 7th that points to a key change. The ear notices the surprise precisely because most chords stay in-key.