Echo a fourth or a fifth. Land the jump without overshooting.

What’s happening.The perfect fourth and perfect fifth are the strongest consonances in tonal music after the octave — they’re the foundation of every cadence, every dominant-to-tonic resolution, and most pop hooks. Untrained singers often nail thirds (small jumps) but overshoot fourths and fifths because the larger gap recruits more breath support and the motor calibration is coarser. The 2.0-second hold inside ±50¢ exposes overshoot — you can’t land “close enough then settle” if you have to commit for a full second.

Why mix P4 with P5, why both directions. The interval between P4 and P5 is exactly one semitone — they share a starting note but resolve differently. Mixing them prevents you from building a single “wide jump” reflex; you have to discriminate. Adding direction randomization rules out kinaesthetic memory: an ascending P5 feels different from a descending P5 in the larynx, but the interval has to be the same in your ear.

Why this is the bridge to harmony. P5 is the tonic-dominant relationship — the most important interval in Western music. Lock P5 echoing here and tonic-dominant-arpeggio (1-3-5-3-1 in two keys) opens up. P4 is its inversion and the cornerstone of suspensions and plagal cadences. Once these two intervals are clean both directions, harmony-over-drone and a-cappella-resolve-tonic become tractable — you can hear “going to V” and “coming back to I” as concrete sounds, not abstract theory.