Make the 2 chord major-dominant and it tonicizes the 5, which then does its normal job. A chain of two dominants stacks the pull toward home — the classic 'five of five'.
hear it in “Salty Dog Blues” · every ragtime turnaround
Lead-in — how players set it upApproached from 1 or 6-, setting up a double cadence.From the turnaround: 6⁷ feeds 2⁷ in a dominant chain.Or borrow the ii–V of 5: 6-⁷ before the 2⁷.Follow — where it usually goes5⁷ does its normal job — or gets delayed by a sus.Land 5 as a half cadence and hang there for drama.Or slide in the tritone sub for 5⁷'s job: b2⁷ down to 1.
Over the 2⁷, the raised note is the key's ♯4 — lean on it, then step it up to 5's root.Target tones (in C)D7 — lean on F# (3) · C (b7)G7 — lean on B (3) · F (b7)C — lean on E (3)Half-step wiresF# → G · C ↘ B · B → C · F ↘ E