Rarest of the family because 3- is the most remote diatonic stop, which is exactly why it sounds expensive. The 7 chord — normally a diminished afterthought — becomes a full dominant aimed at 3-.
hear it in late-Beatles ballads · barbershop tags
Lead-in — how players set it up4 → 7⁷ is the classic setup — a tritone leap in the bass.From 1, leaping bold — the 7⁷ is pure intent.Or from 2-, a whole-step slide up into the dominant.Follow — where it usually goes3- slides down the diatonic walkway toward home.3- can pivot: treat it as new 2- and lift a whole step.Or fall the lane: 3-, 6-, then the turnaround home.
Over 7⁷, the ♯2 begs upward into the 3- chord's 3rd — one bright grain, quickly resolved.Target tones (in C)F — lean on A (3)B7 — lean on D# (3) · A (b7)Em7 — lean on G (b3) · D (b7)Half-step wiresF → F# · C ↘ B · D# → E · F# → G