Hear a cadence. Sing where it wants to rest.
Why this matters: every melody pulls toward its tonic. Once you can find it with your voice (not a piano), you can transpose, harmonize, and improvise from any starting note — Kodály solfège lives on this skill.
10 trials. Each opens with a I-IV-V-I cadence, then a phrase that ends off-tonic. Sing the tonic and hold within ±50¢ for 2.0s. Octave-equivalent counts. Hit 8 to pass.