On Little Seeds, Shovels and Rope (out October 7 on New West) pushes the envelope in both directions. The noisy, propulsive songs are noisier and more propulsive than ever, as the album-opening, wickedly backbiting “I Know” and the devastating “Invisible Man” attest. And the quieter, more reflective material shows the duo’s command of subtlety as well as sonic artillery, with “St Anne’s Parade” and “Mourning Song” combining reflective depth with melodic craft. Storytelling songs such as “Botched Execution” and “Missionary Ridge” remain one of the duo’s strengths as well, though on their third album the personal stories of Michael Trent and Cary Ann Hearst provide the album’s dominant thread, as parenthood and the decline of a parent spark powerful feelings at both ends of the life cycle. Their husband-and-wife harmonies are the spikiest since X’s John and Exene, and their stripped-down instrumental interplay simply bristles. Two spoken word cuts and the secular hymn of “This Ride,” with its handclap heartbeat at the end, bring the song cycle to a full-circle close that is as stunning as it is satisfying. You’d think the two-person band format would suffer from diminishing returns, from the White Stripes to Black Keys to Shovels and Rope, but this blasts open the gates to limitless possibilities.