The diatonic 3- gets its third raised, becoming a dominant 7 that drags the ear to the relative minor. One borrowedleading tone, maximum drama. This is the FM7 → A7 → Dm7 move — the single biggest signal in any 'romantic' chart.
hear it in “Georgia on My Mind” — the canonical 3⁷ → 6-
Lead-in — how players set it upUsually grows out of a settled 1 or a 4 → 3- descent.Or from the turnaround — 2-⁷ dips before the 3⁷ lifts.A held 1 works too; the secondary dominant is the first event.Follow — where it usually goes6- almost always walks the lane: 2-, 5⁷, home.Or resolve deceptively — 3⁷ to 4 instead, tension unpaid.Chain it: 6- becomes the start of a falling-fifths run.
Raise the key's 5 to ♯5 over the 3⁷ — that's the chord's own 3rd — then resolve it up a half step into the 6-.Target tones (in C)Cmaj7 — lean on E (3) · B (7)E7 — lean on G# (3) · D (b7)Am7 — lean on C (b3) · G (b7)Half-step wiresC ↘ B · G → G# · G# → A · B → C