dispelledIntervals
An interval is the distance between two notes. Intervals are the atomic vocabulary of music theory — chords are stacks of intervals, scales are a sequence of intervals, and melodies move through intervals. More practically: if you can hear intervals, you can figure out melodies by ear and understand why chords have the character they do.
All Twelve Intervals
| Semitones | Name | Abbreviation | Example from C | Sound |
|---|---|---|---|---|
| 0 | Unison | P1 | C → C | Same pitch — perfect consonance |
| 1 | Minor 2nd | m2 | C → D♭ | Strongly dissonant, unstable — half step |
| 2 | Major 2nd | M2 | C → D | Mildly dissonant — whole step, scale motion |
| 3 | Minor 3rd | m3 | C → E♭ | Soft consonance — minor quality |
| 4 | Major 3rd | M3 | C → E | Bright consonance — major quality |
| 5 | Perfect 4th | P4 | C → F | Pure, stable — though somewhat hollow |
| 6 | Tritone | TT / A4 / d5 | C → F#/G♭ | Maximum dissonance — exactly half an octave |
| 7 | Perfect 5th | P5 | C → G | Strongest consonance after unison/octave — open, powerful |
| 8 | Minor 6th | m6 | C → A♭ | Soft, bittersweet consonance |
| 9 | Major 6th | M6 | C → A | Warm, open consonance |
| 10 | Minor 7th | m7 | C → B♭ | Mild dissonance — the jazz colour note |
| 11 | Major 7th | M7 | C → B | Sharp dissonance — one step below octave, creates tension |
| 12 | Octave | P8 | C → C | Perfect consonance — same pitch class |
Interval Quality
Quality precisely specifies the interval size:
- Perfect — applies to unison, 4th, 5th, octave. These don't have a major/minor version — they're "perfect" in both major and minor scale contexts. A perfect 5th is always 7 semitones.
- Major / Minor — applies to 2nds, 3rds, 6ths, 7ths. Major is always one semitone larger than minor.
- Augmented — one semitone larger than perfect or major. Augmented 4th = 6 semitones (tritone).
- Diminished — one semitone smaller than perfect or minor. Diminished 5th = 6 semitones (also a tritone).
The Tritone
Six semitones — exactly halfway through the octave. Augmented 4th and diminished 5th are enharmonically the same interval. It's the most dissonant interval in Western music, and the engine of tonal harmony:
In G7: B (major 3rd of G7) and F (minor 7th of G7) are a tritone apart. This tritone wants to resolve: B resolves up by half step → C (tonic's root) F resolves down by half step → E (tonic's major 3rd) Inward resolution: F↓E, B↑C → resolves to Cmaj (I chord) The tritone substitution works because D♭7 has the same tritone (C♭=B, F) just with 3rd and 7th swapped — same resolution energy, different bass.
Consonance and Dissonance
| Category | Intervals | Character |
|---|---|---|
| Perfect consonance | Unison, octave, perfect 5th | Completely stable, open, powerful |
| Imperfect consonance | Major/minor 3rd, major/minor 6th | Stable but warm, characterful — the sounds of chords |
| Mild dissonance | Major 2nd, minor 7th, perfect 4th (in some contexts) | Some tension, but often acceptable as resting points |
| Sharp dissonance | Minor 2nd, major 7th | Strong tension, wants immediate resolution |
| Maximum dissonance | Tritone | Most tense interval — drives harmonic resolution |
Compound Intervals
Intervals larger than an octave are compound intervals — the same class as their simple equivalent plus an octave:
9th = octave + 2nd (same pitch class as 2nd) 10th = octave + 3rd 11th = octave + 4th (same pitch class as 4th) 12th = octave + 5th 13th = octave + 6th (same pitch class as 6th) Jazz chords (maj9, 7#11, 13) are named for compound intervals. Cmaj9 = C E G B D — the D is a major 9th (= major 2nd an octave higher) above C. C13 = C E G B♭ D A — the A is a major 13th (= major 6th up an octave) above C.
Inversion of Intervals
Invert an interval by moving the lower note up an octave (or upper note down): Perfect 5th → Perfect 4th (5 + 4 = 9, perfect stays perfect) Major 3rd → Minor 6th (3 + 6 = 9, major ↔ minor) Major 7th → Minor 2nd (7 + 2 = 9) Tritone → Tritone (6 + 6 = 12 = octave — tritone inverts to itself) Formula: semitones of interval + semitones of its inversion = 12 Quality: major ↔ minor, perfect ↔ perfect, augmented ↔ diminished
Ear Training Reference
Associate each interval with a song you know well — hearing-first learning internalises intervals much faster than drill:
| Interval | Ascending reference | Descending reference |
|---|---|---|
| m2 | "Jaws" theme, "Pink Panther" (first two notes) | "Joy to the World" (first drop) |
| M2 | "Happy Birthday" (first two notes), "Frère Jacques" | "Mary Had a Little Lamb" (first drop) |
| m3 | "Smoke on the Water" (riff), "Greensleeves" | "Hey Joe" (first two notes) |
| M3 | "When the Saints Go Marching In" (first leap), "E.T." (flying theme) | "Norwegian Wood" (opening) |
| P4 | "Here Comes the Bride," "Amazing Grace" | "Eine Kleine Nachtmusik" (first leap) |
| Tritone | "The Simpsons" theme, "Maria" (West Side Story, opening leap) | "Black Sabbath" (title riff) |
| P5 | "Star Wars" theme (opening brass), "Twinkle Twinkle Little Star" | "Feelings" (opening) |
| m6 | "The Entertainer" (opening), "Because" (Beatles) | "The Entertainer" (second phrase) |
| M6 | "My Bonnie Lies Over the Ocean" (first leap), NBC chimes | "Nobody Knows the Trouble I've Seen" |
| m7 | "Star Trek" original theme (first leap), "Somewhere" (West Side Story) | "Watermelon Man" (opening) |
| M7 | "Take On Me" (A-ha, opening leap), "Don't Know Why" (Norah Jones) | Rare — most songs avoid descending M7 |
| Octave | "Somewhere Over the Rainbow" (first two syllables) | "Willow Weep for Me" |
References
- Levine — The Jazz Theory Book
- Aldwell & Schachter — Harmony and Voice Leading
- musictheory.net — Intervals ↗
- ToneDear — ear training for intervals ↗