Music Intervals Explained

What is a Music Interval?

An interval is the distance between two notes. Every melody is built from intervals — the steps between notes create the shape of a tune. Every chord is built from intervals — the gaps between stacked notes define whether a chord sounds major, minor, dim, or aug. Learning intervals is one of the most important steps in understanding music theory.

Half Steps and Whole Steps

The half step (semitone) is the smallest interval on a standard keyboard — the distance from any key to the very next key. The whole step (whole tone) skips one key, equal to two half steps. These two intervals are the building blocks of all scales and larger intervals. C to C# is a half step. C to D is a whole step.

Tip Count semitones on the keyboard first, then name the interval. This keeps the math grounded in something visible.

Thirds — The Building Blocks of Chords

A major third spans 4 semitones (like C to E). A minor third spans 3 semitones (like C to E♭). These two intervals are the most important in harmony. Stack a major third then a minor third and you get a major triad. Stack a minor third then a major third and you get a minor triad. Almost every chord you'll ever play is built from combinations of these two intervals.

Tip If an interval sounds warm and bright, it's likely a major third. If it sounds slightly darker, it's probably a minor third.

Perfect Intervals — The Stable Sounds

Perfect intervals — the perfect fourth (5 semitones), perfect fifth (7 semitones), and octave (12 semitones) — sound especially pure and stable. They've been called 'perfect' for over a thousand years because of how consonant they are. perfect fifths are the sound of power chords in rock and the foundation of classical harmony.

Tip Perfect fifths are the most stable-sounding two-note combination after the octave itself.

Consonance and Dissonance

Some intervals sound restful and settled — these are consonant. Others create tension and feel like they need to resolve to a more stable sound — these are dissonant. This push and pull between tension and resolution is at the heart of how music creates emotion. The tritone (6 semitones, like C to F#) is the most dissonant interval and drives much of the harmonic movement in Western music.

Tip If an interval sounds like it wants to move somewhere else, you're probably hearing dissonance.

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