From intervals all the way to jazz harmony. Every stop is clickable and audible — the first button you press turns the sound on.
① Intervals: the distance between two notes
Tap a starting note on the keyboard (say D), then pick an interval and hear what jumping up from there sounds like.
Tap a starting note → tap an interval
Where you will meet itA major 3rd is the sunshine of a major key, a minor 3rd its melancholy; the perfect 5th is the skeleton of power chords and bass lines;
the augmented 4th (tritone) is the tension at the heart of a dominant 7th, and also the reason a 2-5-1 wants to resolve.
An interval’s name = Numbera number (how many staff steps it spans) plus Qualitya quality (the actual number of semitones). Six semitones is six semitones, but
written F→B it is an augmented 4th, written F→C♭ it is a diminished 5th. The spelling decides the name; the ear hears the same thing.
Quality
Applies to
Rule
Examples (all starting from C)
Perfect
unisons · 4ths · 5ths · octaves
The most stable family — no major or minor about it
C→F perfect 4th, C→G perfect 5th
Major
2nds · 3rds · 6ths · 7ths
The version built into the major scale
C→E major 3rd, C→A major 6th
Minor
2nds · 3rds · 6ths · 7ths
A major interval squeezed by a semitone
C→E♭ minor 3rd, C→B♭ minor 7th
Augmented
Any interval
A perfect or major intervalstretch againsemitone
C→F♯ augmented 4th, C→G♯ augmented 5th
Diminished
Any interval
A perfect or minor intervalsqueeze againsemitone
C→G♭ diminished 5th, C→B𝄫 diminished 7th
A rule of thumb: diminished ← minor ← major → augmented (2nds, 3rds, 6ths, 7ths); diminished ← perfect → augmented (unisons, 4ths, 5ths, octaves).
Each arrow is one semitone. The three quality changes jazz uses most: augmented 4th / diminished 5th (the tritone), diminished 7th (the dim7 chord), and augmented 5th (the augmented chord).
② A field guide to seventh chords: maj7 · 7 · m7 · half-diminished · diminished (plus the whole-tone scale)
Tap a root on the keyboard, then a chord type. You hear it arpeggiated and then blocked, with the formula and its uses shown alongside.
③ Diatonic chords: the seven chords native to one major key
Take every note of a major scale as a root, stack a 3rd, another 3rd and another 3rd on top, and you get the seven diatonic seventh chords — the raw-materials store of jazz harmony. Pick a key and try it:
Notice something?The dashed box around iim7, V7 and Imaj7 is where 2-5-1 comes from — it was never invented,
it was simply picked out of the diatonic chords as the three most eager to get home. The seventh chord, m7♭5 (half-diminished), is the first leg of a minor 2-5-1.
How to use this — diatonic chords are the alphabet for writing and working out songs
① Roman numerals are a universal language: calling chords I, ii and V instead of C, Dm and G means one progression works in every key — it is how musicians talk to each other and transpose on the spot.
② 90% of pop songs live inside these seven: Once you can hear which degree you are on, you can work out the chords and comp behind anyone.
③ A map for improvising: Knowing you are on V7 tells you the ♭9 is available and that it wants to resolve to I. Diatonic chords tell you which notes are family in this bar. Listen to the three most common progressions below: