Interval Ear Training — Thirds and Sixths

Thirds and Sixths — Close and Wide Harmony

Thirds and sixths are inversions of each other — flip a 3rd upside down and you get a 6th.

• m3 (minor 3rd, 3 half steps) inverts to M6 (major 6th, 9 half steps)
• M3 (major 3rd, 4 half steps) inverts to m6 (minor 6th, 8 half steps)

Thirds produce close harmony — notes are near each other, creating a rich blend. Sixths produce wide harmony — notes are spread apart, creating an open, airy sound.

Both are considered consonant intervals and are the foundation of vocal harmonies and chord voicings across all styles of music.

Comparing Thirds and Sixths

Study these four intervals ascending: m3, M3, m6, M6. Notice how the thirds sound compact while the sixths sound spacious. Follow the inversion relationship — m3 becomes M6 when flipped.

Identify Thirds and Sixths by Sound

• Play each interval and identify whether it is a third or a sixth
• Compare minor and major variants — minor intervals sound darker
• Try singing the top note before playing it
• Notice how m3 and M6 share an inversion relationship