With its dozen-plus members and strange instrumentation, Nashville's Lambchop has long demonstrated a propensity for surprise. This makes describing the band particularly difficult: Just when you think you have it figured out, Lambchop pulls its tent pegs and moves on. The group's most radical shift occurred after its How I Quit Smoking album drew notice as one of the most adventurous entries in the alt-country genre. As if unwilling to be categorized, Lambchop responded by playing down the slide guitars and heading in an utterly unpredictable new direction: soul music. On Thriller and What Another Man Spills, the group explores the sounds of Stax and Curtis Mayfield, yet both albums sound like tentative explorations compared to the fully formed vision of Nixon. With a lush string section serving as an impressive counterpart to the languid horns, gentle chicken-scratch guitars, and singer Kurt Wagner's low, warm voice, Nixon sounds like the Superfly soundtrack recorded in a different dimension, one in which Mayfield and Marvin Gaye met up with Lawrence Welk for an impromptu jam session. "Up With People" combines so many disparate influences (including a gospel choir) that the elements borrowed become something new entirely, while "What Else Could It Be?" transcends Wagner's stretched-thin falsetto to evoke the stirring love-me anthems of the great soul men from the '70s. On a ballad-heavy album, "The Distance From Her To There" and "The Book I Haven't Read" still stick out, adding to the thematic inertia. As for the evocative title, it could just be a confusing, winking canard, or maybe Nixon really is a concept album about the era of America's most disgraced president. Either way, it's infused with such beauty, grace, and wistfulness that feelings of nostalgia necessarily ensue. With Nixon, a drowsy near-masterpiece, Lambchop creates timeless, classic music. But the fact that the disc ends on a note as dark as "The Butcher Boy" adds yet another element of ambiguity, casting cynical doubt on the uplifting strains of the songs before it. Love does work in mysterious ways.