You can’t blame Portishead’s cigarette-junkie songbird, Beth Gibbons, for lying low the past four years. Shortly after she defined modern-hipster mood music on 1994’s indelible Dummy, the pop world was suddenly lousy with generic divas getting misty over dollar-store ”trip-hop.” Possibly a response to seeing her persona co-opted, this import-only solo debut unspools like a reel of assorted character studies. Rustin’ Man, a.k.a. ex-Talk Talk bassist Paul Webb, swaps Portishead’s haunted beatscapes for settings where beats are subtle or invisible, from drifting folk (the Nick Drake-y ”Drake”) to symphonic soul (”Tom the Model”). And Gibbons conjures a roomful of weathered voices — some husky and vibrato-shaken, others frail and clean-lined — by turns echoing Nico, Dusty Springfield, Marianne Faithfull, Polly Jean Harvey, Bryan Ferry, and her beloved Billie Holiday without ever sounding derivative. The songwriting isn’t always as artful as the renderings. Yet, like Beck’s recent Sea Change (an LP that should take this one on a date, preferably someplace fun), it cultivates a seamless, sumptuous melancholy. DON’T HOLD YOUR BREATH Portishead are now recording their long-awaited third studio set.