Well, the phrase “chip off the old block” didn’t appear for no reason, and these chips fall where they may — in this case, a clear and beautiful bed of harmony-driven folk. Abigail and Lily Chapin are daughters of three-time Grammy winner Tom Chapin, grandkids of jazz drummer Jim and nieces to singer-songwriter Harry Chapin. The female duo has cropped up on recordings by Will Oldham and backed She & Him on their most recent tour, but as Two shows, they’re far from understudies. Their training in shape-note singing and English folk balladry rolls out on the stunning a cappella “Sweet Light,” and “Birds In My Garden” tumbles along as a fireside dirge before a mid-tune vocal break envelops you in sunny delirium. The Chapin Sisters perform a free, all-ages show at ear X-tacy (2225 Bardstown Road, 452-1799) on Tuesday, Nov. 16.