On their eponymous debut, the Atlanta-based folk-rock duo Indigo Girls crystallized their distinctive sound: bouncing acoustic guitar and raw close harmonies capturing their charmingly youthful verve. This is clearest on the mega-hit “Closer to Fine,” a beckoning, building paean to hope, and “Secure Yourself,” where Amy Ray and Emily Saliers braid their earthy and celestial voices in a hypnotic spiritual. The rock-laced “Kid Fears” showcases their potent storytelling (with a cameo from R.E.M.’s Michael Stipe), while “History of Us” reveals the pair’s gentler, quixotic side.