Intervals · Jazz Wiki

An interval is just the distance between two notes — how far one pitch sits from another. Everything you play or hear in jazz is built from these distances: a chord is a stack of intervals, a scale is a chain of them, and a melodic line is a sequence of them. Learn to hear and spell intervals fast, and you’ve unlocked the alphabet the whole music is written in.

Two numbers, not one: size and quality

Every interval has two properties that both matter. The size is the letter-name count — C up to E spans C, D, E, so it’s a 3rd, no matter how those letters are altered. The quality is the exact number of half steps involved, and this is where Half Steps and Whole Steps does the real work: it tells you whether that 3rd is major (4 half steps) or minor (3 half steps). Quality labels come in families — perfect (unisons, 4ths, 5ths, octaves), major/minor (2nds, 3rds, 6ths, 7ths), and augmented/diminished when you push a semitone past major/perfect or below minor/perfect.

The interval table you actually need

Here are all the intervals inside one octave, spelled from C so you can sing and check them against a keyboard:

Interval	Half steps	Example from C
Minor 2nd	1	C–D♭
Major 2nd	2	C–D
Minor 3rd	3	C–E♭
Major 3rd	4	C–E
Perfect 4th	5	C–F
Tritone (Aug 4th/Dim 5th)	6	C–F♯ / C–G♭
Perfect 5th	7	C–G
Minor 6th	8	C–A♭
Major 6th	9	C–A
Minor 7th	10	C–B♭
Major 7th	11	C–B
Octave	12	C–C

Notice C–F♯ and C–G♭ land on the same key on a piano — that’s Enharmonic Equivalence at work, but they function differently depending on which direction they resolve. This particular interval, exactly six half steps, is unstable enough to earn its own note: see The Tritone.

Here’s that table on the staff, each interval built above C:

Why the 3rd and 7th run the show

Not all intervals in a chord pull equal weight. In chord-tone terms, the 3rd and 7th of any chord are its guide tones — the two notes that actually tell you whether you’re hearing major, minor, or dominant. Compare the guide tones across a ii–V–I in C:

Dm7: root D, 3rd F (minor), 7th C (minor)
G7: root G, 3rd B (major), 7th F (minor)
Cmaj7: root C, 3rd E (major), 7th B (major)

Play just those guide tones and you’ll hear the whole The ii-V-I Progression unfold: Dm7’s C slides down a half step to G7’s B, and G7’s F slides down a half step to Cmaj7’s E. That tiny two-note voice-leading — a minor 7th resolving to a major 3rd, built around the tension of the tritone inside G7 — is the engine behind nearly every jazz cadence. This is also the seed of Guide Tones as a practicing concept: strip a tune down to just 3rds and 7ths and you can still hear the changes.

The guide tones stacked as dyads show the G7 tritone (B up to F, six half steps) sitting between the two resolutions:

From simple intervals to everything else

Once you can spell intervals inside an octave, three ideas open up fast. Flip an interval upside down (move the bottom note up an octave) and you get its inversion — a major 3rd becomes a minor 6th, a perfect 5th becomes a perfect 4th — which is exactly what Interval Inversion covers. Stretch an interval past the octave — a 9th, an 11th, a 13th — and you’re dealing with Compound Intervals, the raw material of Chord Extensions. And whether two notes clash or blend is a question of Consonance and Dissonance: minor 2nds and tritones are restless, thirds and sixths are sweet, and Triads and Seventh Chords are simply intervals chosen and stacked to control exactly how much of each you get. Even The Overtone Series — the physics behind why a perfect 5th sounds so stable — traces back to these same interval ratios.

♫ Listen

Bill Evans Trio — “Autumn Leaves” (Portrait in Jazz, 1959): in the opening minute, Evans’ left-hand voicings move by 3rds and 7ths under the melody — track how the guide tones step down chromatically as the chords change.
Miles Davis — “So What” (Kind of Blue, 1959): the famous piano-and-bass intro stacks perfect 4ths instead of 3rds, a quartal sound built from a completely different interval than the usual tertian chord — a good ear-opener for how much one interval choice changes the color.