Minor Third Interval

minor third overview

A minor third spans three half steps. From C, for example, a minor third up is E♭. The number in its name counts the letter names it covers, including both ends: from C to E♭, C D E is three, so it is a third. The three half steps make it minor. With one half step more, C to E, it would be a major third.

Lesson Steps

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The minor third is the bottom of every minor chord (C to E♭ in C minor), and it also sits on top of every major chord (E to G in C major). On its own it has a softer, darker quality than the major third, and it is one of the first intervals the ear recognizes in a melody.

On the keyboard, a minor third always has two keys between its two notes. Depending on where it starts, those notes can fall on white or black keys, which gives it four different shapes.

The shapes of the minor third on the piano

Each shape sits a little differently under the hand, so it is worth knowing them all. Under each keyboard, the same notes are on the staff: played together, then up, then down.

White key to black key: C to E♭

Minor thirds that share this same shape are C–E♭, F–A♭, and G–B♭. There are two keys in between (one white, one black).

White key to white key: D to F

Minor thirds that share this same shape are D–F, E–G, A–C, and B–D. There are two keys in between (one white, one black).

Black key to white key: C♯ to E

Minor thirds that share this same shape are C♯–E, F♯–A, and G♯–B. There are two keys in between (one white, one black).

Black key to black key: E♭ to G♭

Minor thirds that share this same shape are E♭–G♭ and B♭–D♭. There are two keys in between, all white.

Reading the minor third on the staff

A third goes from a line to the next line up, or from a space to the next space. Both notes are on lines, or both are in spaces. That stays true whatever the accidentals are: every third looks like a third, and the accidentals tell us its quality.

This is what makes intervals so useful for reading. Rather than naming every note from the clef, we read from one note to the next: once we know where we are, the shape on the staff tells us how far to move. Reading this way is relational rather than absolute, and it is much faster.

It works the same in the treble and bass clef, and at any height on the staff, so a reader who knows the look of a third recognizes it everywhere.

The minor third in the hand

In melodies and five-finger patterns, a third often skips a finger: 1 and 3, 2 and 4, 3 and 5. One note is skipped on the staff, and one finger is skipped in the hand.

The spacing on the staff and the spacing in the hand belong together. In a five-finger pattern, a step on the staff is often the next finger, and a skipped note a skipped finger, so the distance we see becomes a distance we feel.

Inverting the minor third

If we move the lower note up an octave (or the upper note down one), a minor third becomes a major sixth: C to E♭ turns into E♭ to C. The numbers of an interval and its inversion add up to nine, and their half steps to twelve (3 + 9). Minor becomes major.

On the keyboard the shapes swap as well: a white-to-black shape inverts to a black-to-white one, and a white-to-white shape stays white to white.

Practice the minor third

Play the first shape, C to E♭, together and then one note after the other, and listen to the sound before moving on.
Find the same shape at every place it occurs on the keyboard (the lists under each image), then the other shapes. Notice how the hand changes as the keys change color, while the sound stays a minor third.
Play a minor third up from all twelve keys, naming the upper note as we go.
Read it: look for minor thirds in a piece we know, and before playing each one, name the interval from its look on the staff.
Once the shapes are reliable, play the interval without looking at the hands, feeling the span between the fingers.

Avoid common mistakes with the minor third

Judging the quality by key color. D–F and C–E are both white-to-white thirds and look the same on the staff, but D–F has one black key between the notes and C–E has two. Counting half steps, three for minor and four for major, settles it.
Counting keys instead of half steps. The starting key isn’t counted: from C, the first half step is C♯.
Reading every note from the clef. Naming each note separately is slow. Reading the interval from the previous note is what lets the eye stay ahead of the hands.