For a growing number of rappers, music opens the door to a career in acting. But for Mos Def, who has already established himself on the stage and screen (big and small) with performances in “Topdog/Underdog,” “The Italian Job,” and the HBO film “Something the Lord Made,” a continued career in rap is beginning to look like an exercise in acting.

Waiting in the long snaking line outside B.B. King’s for Wednesday night’s sold-out concert, a line that was disproportionately female for a hip-hop show, I talked to several fans about the man and the music. To a person, they praised Black Star, his influential late 1990s partnership with Talib Kweli, admired “Black on Both Sides,” his first solo album released six years ago, and claimed to be “just getting into” “The New Danger,” his latest offering, which came out late last year.

Oh, and they all volunteered the fact that they are head over heels in love with the man.

Mos wore the uniform of a thug rapper – a shirt buttoned only at the collar, vato loco style; a baggy black panthers basketball jersey underneath – but came off looking like a Pixar character nonetheless. He has deep crevice dimples, enormous ventriloquist-dummy eyes, and a warming smile. Women dragged their boyfriends to the foot of the stage for a closer look.

The dirty little secret of Mos’s multifront talent offensive is that, as a rapper, he isn’t very talented. Talib Kweli was by far the stronger wordsmith in Black Star; Mos got by on charisma – just as he’s been doing ever since.

Except for a catchy Kanye West soul sample on “Sunshine,” his beats Wednesday were undistinguished – and often indistinguishable – and his rhymes were muddled. Rather than free styling between songs, the way another rapper might, Mos performed the lyrics to the next song a capella, then again with the music. Even had they been off the top of his head, they weren’t very impressive.

It’s just as well, then, that the bulk of his new music tends towards rock. “This is the sound of ghetto rock,” Mos said, leading the crowd in chant. For the last few years, he has been working with an all-black rock band called Black Jack Johnson, with the idea of reclaiming rap-rock for black music, and redeeming it after Limp Bizkit and Linkin Park. The long-anticipated album never materialized, but rock has found its way into his beats, which included crunchy rock riffs, funk, spacey guitar, and electric blues samples.

The approach worked occasionally, as on “Zimzallabim,” which sounded a little like the old Public Enemy/Anthrax collaboration, and “Black Jack,” a blues-influenced sing-along tribute to the first black heavyweight boxing champion and proto-rap-star Jack Johnson. But it also made Mos look more like a hype man than a first-rate rap star.

If the show did little to boost his stature as a rapper, at least it confirmed his acting chops. He is badly miscast in the role, but did a decent job of selling it, only breaking character a few times to clown and mug for the audience. As he explained in one especially Inside the Actor’s Studio moment: “You can’t be weak up here. … You got to have a little bit of a swagger,” the smile vanishing, momentarily, from his face.

Mos Def will perform again tonight at 11 p.m. (237 W. 42 Street, between Seventh and Eighth Avenues, 212-997-4144).