Linda Ronstadt’s rich alto and Emmylou Harris’ crystalline soprano intertwine to mesmerizing effect on these covers and originals. The duo reinterpret Sinead O’Connor’s “This Is to Mother You” as a tinkling lullaby with a heartbeat rhythm, while Leonard Cohen’s “Sisters of Mercy” sways to mandolin, accordion, and sweet, sweet harmonies. Things get turned up a notch with the shuddering vibrato guitar of “Falling Down,” while “Sweet Spot,” a sly and spacious groove driven by stuttering bass, is cowritten by Harris and Luscious Jackson’s Jill Cunniff.