Intervals: The Building Blocks of Music

§ 01What an Interval Is

An interval is the distance between two pitches. That's it. When you play C and then E, the distance between them — four semitones — is a major third. When you play C and G at the same time, the interval is a perfect fifth.

Intervals are the atoms of music. Every melody is a series of intervals. Every chord is a stack of them. Every scale is a specific pattern of them. Understanding intervals means understanding why music sounds the way it does.

Intervals have two key properties: a number (second, third, fourth…) and a quality (perfect, major, minor…). Together they give you a precise name — "major third," "perfect fifth," "minor seventh."

§ 02Two Parts of an Interval Name

Every interval name has exactly two parts: the number and the quality.

Together: "major third." Never say just "third" — there are four kinds (major, minor, augmented, diminished). Always include the quality.

§ 03The Number: Letter Counting

Count letter names from bottom to top, including both endpoints. Ignore sharps and flats — they don't affect the number.

C to E♭ is still a third — E♭ is still the letter E. C to D♯ is a second. Always count letter names, never semitones alone, to find the number.

§ 04The Quality

Intervals fall into two families based on their number: the perfect family (unisons, fourths, fifths, octaves) and the major/minor family (seconds, thirds, sixths, sevenths).

§ 05The Major-Scale Method

The fastest way to identify any interval: compare the top note to the major scale built on the bottom note. If the top note is in that major scale, the interval is either perfect (for 1, 4, 5, 8) or major (for 2, 3, 6, 7). If it's one semitone lower, it's minor. Two semitones lower, diminished. One semitone higher, augmented.

§ 06Every Interval Within One Octave

There are 13 distinct intervals from unison (0 semitones) to octave (12 semitones). Use the explorer below to hear each one, see it on the keyboard, and read its character.

§ 07Augmented and Diminished Intervals

Beyond major, minor, and perfect lie augmented (one semitone wider) and diminished (one semitone narrower). They arise most often when spelling intervals correctly across accidentals.

§ 08The Tritone

The tritone — exactly 6 semitones — is one of music's most dramatic intervals. Medieval theorists called it diabolus in musica ("devil in music") and avoided it in sacred compositions. It's the only interval that perfectly bisects the octave.

It has two enharmonic spellings: the augmented fourth (C–F♯, spelled upward) and the diminished fifth (C–G♭, spelled as a compression). Both are exactly 6 semitones. Context determines which name is correct.

The tritone is essential to dominant seventh chords — the tension between the third and seventh (e.g. E and B♭ in G7) creates a tritone that demands resolution to the tonic. This is the engine of tonal harmony.

§ 09Harmonic vs Melodic Intervals

A harmonic interval is both notes sounding simultaneously — the interval you hear in a chord. A melodic interval is the notes played sequentially — the interval you hear in a melody line.

The interval name is the same whether harmonic or melodic. C–G is always a perfect fifth. But the ear perceives them differently — a harmonic P5 sounds stable and full; a melodic P5 ascending sounds bold and decisive.

§ 10Consonance and Dissonance

Consonant intervals sound stable and resolved. Dissonant intervals sound tense and want to move. This isn't a value judgment — dissonance is essential; it creates the tension that makes resolution meaningful.

§ 11Interval Inversion

Invert an interval by moving the bottom note up an octave (or the top note down). The interval flips. Two simple rules govern inversions:

• Numbers sum to 9 — a 3rd inverts to a 6th (3+6=9), a 4th to a 5th (4+5=9).
• Qualities flip — major ↔ minor, augmented ↔ diminished, perfect stays perfect.

The tritone inverts to itself — it's equidistant from both ends of the octave. Augmented fourth (C–F♯) inverts to diminished fifth (F♯–C) — both 6 semitones.

§ 12Compound Intervals

A compound interval spans more than an octave. It's named by adding 7 to the simple interval's number (since an octave = 8, and 8−1=7). The quality stays the same.

§ 13Enharmonic Intervals

Two intervals are enharmonic when they contain the same number of semitones but have different names and spellings. Context — the key you're in — determines which name is correct.

§ 14Ear Training: Songs for Every Interval

The fastest way to learn intervals by ear: associate each one with a song you already know. Hear the first two notes of the melody — that's the interval. Train your ear to recognize the song, and you recognize the interval.

§ 15Intervals Inside Chords

Every chord is built by stacking intervals. The specific intervals you stack determine the chord quality. Understanding this gives you complete control over chord construction and color.

§ 16Why Intervals Matter

Intervals aren't just theory vocabulary. They're the mechanism behind everything you hear in music. When a melody moves and you feel something — a leap of a major sixth creating a yearning, a stepwise minor second creating tension — that's intervals working on you.

Composers and songwriters think in intervals. They choose intervals deliberately to get specific emotional effects. A minor third descent in a vocal line feels different from a perfect fourth descent. The difference isn't arbitrary — it's physics and perception.

For pianists specifically: knowing intervals means you can read chord symbols instantly, transpose melodies on the fly, and understand why a voicing sounds good. The piano keyboard makes interval distances visual — you can see a fifth, a third, an octave as a physical hand shape.

"Intervals are the grammar of music. Once you know the grammar, you can read any sentence."

§ 17Common Mistakes

§ 18Practice Exercises

§ 19Ear Training Quiz

Test your ears. A random interval from a random root note plays — first harmonically, then melodically. Identify it from four choices.

§ 20FAQ