What is an interval?
An interval is the distance between two notes. Melodies are strings of intervals, chords are stacks of them, and scales are patterns of them. If you can name any interval quickly, chord symbols, key signatures and ear training all get easier.
Every interval has two parts, and both come from simple counting: a number and a quality.
Step 1: the number
Count letter names from the lower note to the upper one, including both ends. C up to E passes through C-D-E, so it is a 3rd. C up to G is C-D-E-F-G, a 5th. The number ignores sharps and flats: C to E, C to E♭ and C to E♯ are all 3rds. The same letter is a unison (1st), and the next one along is an octave (8th).
Step 2: the quality
The number only says how many letters; the quality says how many half steps that span holds. The qualities depend on which kind of interval it is:
- 2nds, 3rds, 6ths and 7ths come as major or minor. Minor is one half step smaller than major.
- Unisons, 4ths, 5ths and octaves are perfect. They have one size.
- Make a major or perfect interval a half step bigger and it is augmented.
- Make a perfect or minor interval a half step smaller and it is diminished.
Here is the rule in one line: major shrinks to minor, minor shrinks to diminished; perfect shrinks to diminished, and both grow into augmented.
| Interval | Half steps | From C | A song to remember it by |
|---|---|---|---|
| Perfect unison P1 | 0 | C | The same note twice |
| Minor 2nd m2 | 1 | D♭ | Theme from Jaws |
| Major 2nd M2 | 2 | D | Do-Re-Mi (Do to Re) |
| Minor 3rd m3 | 3 | E♭ | Smoke on the Water, Greensleeves |
| Major 3rd M3 | 4 | E | When the Saints Go Marching In |
| Perfect 4th P4 | 5 | F | Here Comes the Bride |
| Augmented 4th A4 | 6 | F♯ | The Simpsons theme (tritone) |
| Perfect 5th P5 | 7 | G | Twinkle Twinkle Little Star, Star Wars theme |
| Minor 6th m6 | 8 | A♭ | Love Story theme ("Where do I begin") |
| Major 6th M6 | 9 | A | My Bonnie Lies Over the Ocean |
| Minor 7th m7 | 10 | B♭ | Somewhere (West Side Story) |
| Major 7th M7 | 11 | B | Take On Me (chorus leap) |
| Perfect octave P8 | 12 | C | Somewhere Over the Rainbow |
Why spelling matters
On a piano, C to G♯ and C to A♭ are the same two keys, but they are different intervals. Counting letters, G♯ is a 5th above C (C-D-E-F-G), so C to G♯ is an augmented 5th. A♭ is the 6th letter, so C to A♭ is a minor 6th. They sound the same but are written differently and behave differently in harmony. This is what the Heavy lift level trains, because correct spelling is how sheet music, chord symbols and key signatures stay consistent.
The tritone is the classic example. Six half steps can be an augmented 4th (C to F♯) or a diminished 5th (C to G♭). The note you pick depends on the key.
How to build an interval
- Find the letter. A 3rd above D is F (D-E-F). A 6th below G is B (G-F-E-D-C-B).
- Count the half steps from the starting note to that letter as it stands. D to F is 3 half steps.
- Adjust with a sharp or flat until the count matches the quality you want. A major 3rd needs 4, so raise F to F♯. A minor 3rd needs 3, so F stays natural.
Shortcut for the major intervals above the lowest note: they are the notes of the major scale starting on it. A major 3rd above D is F♯ because F♯ is the third note of D major.
How to practise
- Warm-up: learn the five landmark intervals (perfect 4th, 5th and octave, major 2nd and 3rd) until you name them without counting.
- Working set: add the minor intervals and start from notes with sharps and flats. Count letters, then half steps, every time.
- Heavy lift: add augmented and diminished, descending intervals and exact spelling.
- Go timed. Two minutes of intervals every day is enough to make them automatic. The answer panel plays the interval and shows both notes on the keyboard so you connect the name, the shape and the sound.
Intervals are the foundation of chords: a major triad is a major 3rd with a perfect 5th, and a minor triad is a minor 3rd with a perfect 5th. See them stacked on the chord finder, practise the other side of the same skill with scale degree names, or learn where the notes live with the piano key trainer.
Frequently asked questions
What is a musical interval?
An interval is the distance between two notes. It has a number (how many letter names it spans, counting both ends) and a quality (perfect, major, minor, augmented or diminished) that says exactly how many half steps it holds.
How do I find the number of an interval?
Count letter names from the lower note to the upper one, counting both. C to E spans C-D-E, so it is a 3rd. C to G spans C-D-E-F-G, a 5th. Accidentals do not change the number: C to E♭ is still a 3rd.
What is the difference between major and minor intervals?
A minor interval is one half step smaller than the major interval of the same number. C to E is a major 3rd (4 half steps) and C to E♭ is a minor 3rd (3 half steps). The same goes for 2nds, 6ths and 7ths.
Why are 4ths and 5ths called perfect?
Unisons, 4ths, 5ths and octaves are called perfect because they sound especially stable and because their sizes are the same in the major and minor scale. They come in one size, not two. Make one a half step bigger and it is augmented; a half step smaller and it is diminished.
What is the difference between augmented and diminished?
Augmented means one half step bigger than major or perfect. Diminished means one half step smaller than minor or perfect. C to G♯ is an augmented 5th and C to G♭ is a diminished 5th.
Is C to A♭ a minor 6th or an augmented 5th?
A minor 6th. A♭ is the sixth letter name counting from C (C-D-E-F-G-A), so it is a 6th. The enharmonic G♯ sounds the same but, with a letter G, would make it an augmented 5th. The spelling decides the name.
What is a tritone?
A tritone is six half steps, three whole tones. It is either an augmented 4th (C to F♯) or a diminished 5th (C to G♭), depending on the spelling. It splits the octave exactly in half and sounds tense and unresolved.
How do I learn to hear intervals?
Attach each interval to a song you know (see the table above), then practise naming them by sight first. Once the shapes on the keyboard are automatic, ear training gets much easier because you know what you are listening for.
How do I build an interval above or below a note?
Step one: count the letters (a 3rd above C is E, a 6th below C is E). Step two: add or remove accidentals until the half step count matches the quality. Heavy lift mode drills this in both directions.