Kevin Spacey's acting credentials may have drawn a sold-out house of curiosity seekers to the Somerville Theatre last night, but it was his singing that kept them there. Spacey, who stars as Bobby Darin in the upcoming film ''Beyond the Sea," is on a mission to reintroduce Darin to the public. He's on a 10-city tour performing Darin's songs in front of a big band orchestra. And it's no joke, because Spacey is so enthralled with Darin -- he used to sing Darin's songs into a hairbrush when he was a kid -- that the passion spilled over to the mixed-age crowd, which extended him a heartfelt standing ovation at night's end.
''It was worth the ride down from Bangor!" one woman yelled.
Spacey fielded the remark graciously, which was the way he conducted this entire 90-minute show. He kept the focus on Darin (''We're here to celebrate one of the finest entertainers we've ever had," he said early) and never talked about himself or gave the slightest hint that he was Hollywood royalty after making such films as ''American Beauty" and ''L.A. Confidential."
Performing in a tuxedo, Spacey conveyed all of Darin's personalities -- from teen idol (on ''Splish Splash," ''Dream Lover," and ''Mack the Knife" from the late '50s) to nightclub crooner (''Fly Me to the Moon" and ''My Funny Valentine") and late-period folk singer (Tim Hardin's ''If I Were a Carpenter"). All of these phases spanned a relatively brief career that ended in 1973 when the New York-born Darin died of heart failure at 37.
Spacey is 45, but perhaps buoyed by his acting instincts, he was convincing on each stop of Darin's career. Spacey opened with the snappy swing of ''Hello Young Lovers" and ''Sitting on Top of the World," giving the impression that this was not going to be a dull, formulaic evening. He didn't have the most powerful voice, but he was on pitch throughout and his expressiveness was superb. He made the songs come alive, whether finger-snapping through ''Mack the Knife," scatting to climax ''Beyond the Sea," or capturing Randy Newman's ''Sail Away." He also flashed Darin's mimicking ability on talking impressions of Marlon Brando, Jimmy Stewart, Katharine Hepburn, and Jerry Lewis.
It was thoroughly entertaining -- and Spacey added a number of Darin-related songs that are not in the film. He also was a surprisingly strong bandleader, though he had a lot of help from pianist Roger Kellaway, who backed Darin in the '60s. The rest of the group ranged from an 11-piece horn section (hired locally) to touring members entailing a guitarist, bassist, drummer, and two volcanic singers in Felice Hernandez and Amy Keys, who brought the house down with a gospel flourish on Simon & Garfunkel's ''Bridge Over Troubled Water." A job well done.