Weeks 5-6 · ear · do-mi-sol-mi-do
Sing the home chord one note at a time. All three in tune.
The rule
pass: each note ±50¢ · 8/10 trials
Five anchor dots — do · mi · sol · mi · do — at the major-triad pitches. The emerald arch is symmetric: up the third, up the third, back down the same way. The grey ghost shows the classic untrained miss — a flat third in the middle and a descent that overshoots the target on the way back home. Each anchor has a ±50¢ tolerance band around it.
Hear it first
The arpeggio played in tune, then the same shape with a sagging third — the most common ear mistake, where the mediant pulls toward the minor third by habit. Listen for the bright open feel of a proper major third before you try producing it.
What’s happening.The 1-3-5 arpeggio outlines the tonic chord — the home triad every major-key melody returns to. Singing it cleanly without an instrument means you’ve internalized the major-third (4 semitones) and perfect-fifth (7 semitones) intervals as independent motor targets, not as “the next note up.” Untrained ears can identify a major triad about 60% of the time; producing one from memory is a separate skill.
Why the symmetric 1-3-5-3-1.Going up and back forces you to land on the same notes twice, which exposes drift — if you were a hair sharp on the way up, you’ll hear it when you can’t match it coming down. Each note must hold within ±50¢ for 2.0s, which is enough time for your ear to confirm the landing before the next leap.
Why this is the bridge. Triad fluency is the prerequisite for tonic-dominant arpeggios, scale-degree drills against a drone, and a-cappella resolution to tonic. Most of the harmony work in weeks 9-12 assumes you already hear and produce 1-3-5 on demand — settle it here.
Session ahead
10 trials · hear 1-3-5-3-1, then sing 1, 3, 5 on a hum · each note within ±50¢ held 2.0s · 8/10 to pass.