Major third

The heart of the major triad

The major third is the radiant third of the major chord. With the ratio 5:4 it sounds bright, clear and joyful. The C major triad consists of C, E and G, and the interval C–E is the major third. It conveys the typical bright mood of major.

The fifth partial of every tone is a major third, two octaves above. The major triad is therefore already laid down in every single tone. You can hear this on the guitar: if you touch the string lightly above the 4th fret, a very high tone sounds as a harmonic, at a distance of two octaves and a major third. It sounds pure, bell-like and radiant.

Just or equal-tempered

The just major third (5:4) sounds purer and calmer, because it has no beats, than the tempered third of equal temperament or the older Pythagorean third (81:64). In equal temperament it lies 14 cents higher than in just intonation. Ensembles with flexible pitch, such as string quartets or vocal groups, therefore play and sing it lower than the piano would. In history it was long disputed: in the Middle Ages it was at first treated as a dissonance and only gradually recognised as an imperfect consonance; in the Renaissance it then became firmly part of the musical texture.

On the guitar

On a single string, a major third lies four frets (four semitones) above the starting note. In standard tuning the G string lies exactly a major third below the B string. That is the only “third gap” in the otherwise fourth-tuned guitar and the reason why some chords are fingered a little unusually on the guitar.

Common mistakes

• Confusing it with the minor third: Four semitones against three.
• Doubling the third: In four-part writing the third is not doubled, because its colour would otherwise stand out too much.
• Following the tuner: If you play the third in an ensemble, you tune it by ear until the beating disappears.