Add the 6 beside the 5 and the tonic smiles instead of just sitting there — doo-wop, western swing, early pop. On the 4 chord it's the same trick a string over. (Bonus: 4⁶ is the same four notes as 2-⁷.)
movesthe 5 gains a neighbor a whole step up — warmth, zero tensionsolo·singthe 6 is now a chord tone — end a phrase on it over the tonicon recorddoo-wop endings everywhere — strum 1⁶ and you'll hear ittry itEnd your song on 1⁶ instead of 1. Instant vintage.