Notes and intervals
Major third
A major third is the interval of four semitones, as from C to E: it is what makes a chord major, and on the guitar it spans four frets on one string.
What is a major third?
A major third is an interval of 4 semitones, or two whole steps. It spans three letter names (C, D, E), hence third, and the 4-semitone distance makes it major.
Examples worth knowing: C-E, G-B, D-F#, A-C#, E-G#, F-A. The major third is the note that gives a major chord its bright colour: take it away and the chord is neither major nor minor.
How do you play a major third on guitar?
From any root, three shapes in standard tuning:
- Same string, 4 frets up: C at the 3rd fret of the 5th string, E at the 7th.
- Next string, one fret lower: C at the 3rd fret of the 5th string, E at the 2nd fret of the 4th. Or G at the 3rd fret of the 6th string, B at the 2nd fret of the 5th.
- From the 3rd to the 2nd string, same fret: open G and open B, or C at the 5th fret of the 3rd string and E at the 5th fret of the 2nd.
Spot it in open chords: G# at the 1st fret of the 3rd string in E, E at the 2nd fret of the 4th string in C, C# at the 2nd fret of the 2nd string in A, F# at the 2nd fret of the 1st string in D.
Major third vs minor third: one fret changes everything
The minor third is one semitone smaller. On the guitar that is one fret, often a single finger:
- E to Em: lift the finger off the 1st fret of the 3rd string (G# becomes G).
- A to Am: the 2nd string moves from the 2nd fret to the 1st (C# becomes C).
- D to Dm: the 1st string moves from the 2nd fret to the 1st (F# becomes F).
A major chord stacks a major third, then a minor third (C-E, then E-G). Two major thirds stacked give an augmented chord: C, E, G#.
Exercise: thirds in C major on the G and B strings
Play these note pairs together on the 3rd and 2nd strings, climbing the C major scale:
- C-E: 5th fret and 5th fret (major third)
- D-F: 7th fret and 6th fret (minor)
- E-G: 9th fret and 8th fret (minor)
- F-A: 10th fret and 10th fret (major)
- G-B: 12th fret and 12th fret (major)
The major thirds land on C, F and G: exactly the three major chords of the key (I, IV, V). This is the core of every triad. The guitar triads tool shows where the third sits in each inversion on every string set.
Key takeaways
- Major third = 4 semitones = 4 frets on one string.
- On the next string it is one fret lower; between G and B, the same fret.
- It makes a chord major; one fret lower and the chord turns minor.
- In G7, the third (B) pulls up to C: it is a crucial guide tone.
Frequently asked questions
How many frets is a major third?
Four frets on the same string. On the next string up, the major third sits one fret lower than the root, except between the 3rd and 2nd strings, where it is on the same fret.
Which chords contain a major third?
Major chords (C), dominant sevenths (C7), major sevenths (Cmaj7), sixth chords (C6) and augmented chords (C+). Sus2 and sus4 chords have no third at all, which is why they sound open. To check a chord, enter its notes in the chord identifier.
Is a major third the same as a diminished fourth?
They sound the same (4 semitones) but are spelled differently: C-E is a major third, C-F♭ a diminished fourth. In practice the diminished fourth only shows up in specific places, such as the harmonic minor scale (G# up to C in A minor).
Related terms
Practise in the workshop
Take it from theory to the fretboard
Open the workshop tools and see this idea across the whole neck. Free account, no card needed.