Like much of the so-called classic cinema, “Pitch Perfect” is a triumph of producers and casting directors. There are actors it’s good to see in a movie, regardless of impersonally routine direction and a script with utterly foreseeable action and leaden humor, and this comedy, set in the world of competitive collegiate a-cappella singing, is filled with such actors. I’ve been waiting for a while to see Anna Kendrick, with her blend of tremulous vulnerability, searching intelligence, and steely guardedness, in a starring role (she was the main reason to see “Up in the Air” and “50/50”). Though her leading role here as Beca, a college student—a solitary techno d.j. who, in effect, joins a singing group in order to get out of it—is hardly meaty, it has the essential merit of keeping her onscreen for extended periods of time, and that’s more or less enough. The same is true of her partners in the chirpy enterprise—the flamboyantly gifted comedian Rebel Wilson, the furiously dedicated Brittany Snow, and, really, the whole large cast, who infuse the story’s clichés and broadly drawn characters with energy and emblematic presence—and who, doing their own singing and dancing, seem to have thrown themselves gleefully into the work. They hold the screen for almost two hours, each of them has his or her moments in the spotlight, none wears out a welcome, and the experience is bouncy fun, but, at the end, there’s little left but their faces and voices, the thoughts of what could have been, and the promise of their movies to come.