Notes and intervals
Minor third
A minor third is the interval of three semitones, as from A to C: it gives minor chords their darker colour and spans three frets on one guitar string.
What is a minor third?
A minor third is an interval of 3 semitones, a whole step and a half. Like the major third it spans three letter names (A, B, C), but it is one semitone smaller.
Examples: A-C, E-G, D-F, B-D, C-E♭, G-B♭. Placed above the root, it makes the chord minor: A, C, E is Am. A minor chord stacks a minor third, then a major third: the reverse of a major chord.
How do you play a minor third on guitar?
Three shapes in standard tuning:
- Same string, 3 frets up: A at the 5th fret of the 6th string, C at the 8th.
- Next string, two frets lower: A at the 5th fret of the 6th string, C at the 3rd fret of the 5th.
- From the 3rd to the 2nd string, one fret lower: A at the 2nd fret of the 3rd string, C at the 1st fret of the 2nd.
In open chords: C at the 1st fret of the 2nd string in Am, the open G string in Em, F at the 1st fret of the 1st string in Dm. Each time, it is the note that separates the chord from its major version.
The minor third in scales and chords
The natural minor scale and the minor pentatonic both start with it. In position 1 of A minor pentatonic (5th fret), the two notes on the 6th string, frets 5 and 8, are A and C: a minor third under your fingers from the first note.
Stack two minor thirds and you get a diminished chord: B, D, F. Add a third one (A♭) and you have Bdim7, a symmetrical chord: every note is a minor third from the next, so the same shape repeats every three frets.
Finally, the relative minor of a major key sits a minor third lower: C major and A minor share the same notes.
Exercise: major, minor and the blue note
Alternate A and Am, four beats each, moving only the finger on the 2nd string (2nd fret, then 1st fret). Do the same with E and Em (3rd string) and with D and Dm (1st string). Listen to the colour flip every time.
In blues, the minor third is often bent slightly toward the major third. In A minor pentatonic at the 5th fret, play C at the 5th fret of the 3rd string and push the string up about a quarter tone, without reaching C#. Compare A and Am on the same strings in the guitar triads tool.
Key takeaways
- Minor third = 3 semitones = 3 frets on one string.
- Next string: two frets lower; between G and B: one fret lower.
- It makes a chord minor; stacked, it builds diminished chords.
- The relative minor sits a minor third below the major tonic.
Frequently asked questions
How many frets is a minor third?
Three frets on the same string. On the next string up it sits two frets lower than the root, except between the 3rd and 2nd strings, where it is just one fret lower.
Why does a major chord contain a minor third?
Because chords are built by stacking thirds. C, E, G contains a major third (C-E) and then a minor third (E-G). What matters is the third measured from the root: major for C, minor for Cm (C, E♭, G).
What is the difference between a minor third and an augmented second?
Same sound (3 semitones), different spelling. F to G# is an augmented second: you find it in A harmonic minor (A, B, C, D, E, F, G#), where it creates that exotic flavour. Check how a chord is spelled in the chord identifier.
Related terms
Practise in the workshop
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