Every choir knows the dreaded "break", that audible clunk when navigating between chest and head voice. You can't just "sing through it." You need to condition your laryngeal muscles to tilt smoothly rather than flip abruptly.
Why the Fifth?
A perfect fifth (3:2 frequency ratio) is wide enough to engage your cricothyroid muscles without demanding the extreme coordination of an octave. The slide forces continuous airflow. You can't stop and reset between notes. Your chest-voice muscles gradually hand off control to your head-voice muscles, smoothing out the transition.
How to Execute
Think of this as connecting two notes with a thread of sound.
Setup: Balanced posture, larynx neutral (not hiked up).
Onset: Start on the root (1) with a clean, soft onset. No glottal attack.
Slide up: Travel slowly to the fifth. Picture a rubber band stretching, not climbing stairs. The sound goes forward, not up.
Slide down: Return to the root. Keep that sense of lift even as pitch drops.
Common Problems
Chin lifts on the ascent: You're recruiting swallowing muscles. Watch in a mirror. Keep chin level and imagine air traveling down into your body as pitch goes up.
Sound cuts out mid-slide: Breath pressure dropped. Maintain steady abdominal engagement throughout the entire arc.
"Tight" feels like support: Real support is engagement in your torso while your neck stays free. If your throat is clenching, that's not support.