Not all thirds are created equal. In diatonic harmony, you encounter both major thirds (four semitones) and minor thirds (three semitones) depending on where you are in the scale. Learning to navigate this alternation is essential for singing harmony in any key.
This exercise has you move in parallel thirds above an ascending and descending scale fragment. As the melody moves 1-2-3-4-5-4, you sing 3-4-5-6-7-6 a third above.
Actionable Step: Diatonic Thirds
1. The Sound
Use a bright "Ay" vowel with forward placement. This brighter vowel helps clarify the difference between major and minor thirds. You'll hear the color change more distinctly when using a forward, resonant vowel.
2. The Feel
Major thirds feel warmer and wider. Minor thirds feel cooler and narrower. As you move through the exercise, pay attention to how each third locks in differently. The major thirds (like 1-3 and 4-6) have one sweet spot, while minor thirds (like 2-4, 3-5, and 5-7) have another.
When tuned correctly, major thirds sit about 14 cents flat of equal temperament, while minor thirds sit about 16 cents sharp. You don't need to think about the numbers, just notice the different "lock" sensation for each quality.
3. The Drill
The backdrop plays scale degrees 1-2-3-4-5-4, all half notes. You sing 3-4-5-6-7-6 in parallel motion a third above.
Backdrop (what you hear):
Your part (what you sing):
Move in perfect sync with the backdrop. When it goes up, you go up. When it comes back down, you come back down. The challenge is maintaining accurate intonation as the third quality changes from major to minor and back.
Practice with Vocal Driller
Using the Fader
Start with the fader toward your harmony part so you can clearly hear your thirds. As you gain confidence, gradually shift the fader toward the melody. The real test is maintaining accurate third quality when the backdrop is louder than your guide track.
Listen for the moments when each third locks in. If a third sounds harsh or beats excessively, you're likely singing it with the wrong tuning. Major thirds need to be narrower than piano tuning, minor thirds need to be wider.