In 1978 Willie Nelson released Stardust, an album that drew, deeply and unexpectedly, from the repertoire of the Great American Songbook. Like the earlier crossover work of Ray Charles, Stardust hit a nerve, reaffirming the cross-cultural unity of popular music — it made Nelson a superstar and remains his best-selling work. American Classic is a sequel of sorts, though thirty years down the line we are quite aware of Nelson’s ambitions and omnivorous range; the shock of a country singer romping in Sinatra’s stylistic backyard is long gone. “Shotgun Willie,” the one-time C&W outlaw, is now in his seventies, and the new project reflects the passing years. Unlike its predecessor, American Classic has little of the quality of an event; it’s merely a lovely, resolutely modest take on some sweet and sturdy songs. This time around Nelson left his own band back on the bus, replacing them with such jazz luminaries as pianist Joe Sample and bassist Christian McBride; the famed arranger Johnny Mandel also makes his presence felt on a handful of tracks. But the heady company (Diana Krall and Norah Jones pop by for duets) never draws attention away from a seasoned singer whose relaxed delivery and way-behind-the-beat phrasing have seen him faithfully through the decades. Unassuming pleasures stand in for rousing highs: “The Nearness of You,” “Angel Eyes,” “Come Rain or Come Shine,” are among the warhorses given affectionate dusting-offs. In other words, American treasures as sung by an authentic American treasure.