The Major 6th

9 semitones — warmth and openness

Prove it — just do the practice exercise.
C → A 9 semitones
C (root) A (Maj 6th)
The major 6th = 9 semitones:

• In the 6th chord (e.g. C6 = C + E + G + A)
• Often replaces the 7th for a more open sound
• Enharmonically the same as the diminished 7th

Example: C → A = major 6th

In jazz standards, ending chords are often played as 6 or 6/9 instead of Maj7.