If you’ve ever wondered about how some of those would-be stars get on “American Idol,” here is a film about some who don’t. “Great World of Sound” is a movie about an outfit that buys ads in the papers offering free auditions to new talent, and then tries to sell them a “professional recording session” that will produce a CD allegedly distributed to radio stations and record companies.

To some degree, this offer is real. To a very small degree. We actually even see one of the clients in the “professional” studio. But the real point is to get the hopefuls to show their “commitment” by “investing” $3,000 in their “futures.” We follow two of the Great World salesmen on their odyssey through the cheap motels and fast food grease pits of the South: Martin (Pat Healy), a neat, introverted, worrywart, and Clarence (Kene Holliday), an ebullient African-American who, after spending three years on the streets of Houston, is happy to have this job or any job.

In a way, the movie resembles Albert and David Maysles’ great documentary “Salesman” (1968), about door-to-door Bible salesmen. The salesmen in both films are led to expect much larger rewards than are possible. But “Great World” has another dimension: Although Martin and Clarence are fictional characters, many (but not all) of those who come to audition aren’t in on the joke. They think it’s a real audition: in that sense, they’re as exploited in real life as in the story. (Director Craig Zobel says he got releases from everybody after the fact.)