The late '60s were home to many of the great voices of the 20th century: LBJ and MLK, for example. But neither of them was quite in the same league with RWPG: Ralph Waldo "Petie" Greene: an ex-con who was to become a Washington, D.C.-area DJ, TV host, standup comic and, most importantly, a community activist and voice of the unheard.

How all this came about is the stuff of Talk to Me, a film biography "inspired by a true story" and directed by Kasi Lemmons of Eve's Bayou fame.

Greene (Don Cheadle) is a perennial prisoner in a D.C.-area jail who lives for just two things: conjugal visits from his girlfriend, Vernell Watson (Taraji P. Henson) and his DJ show on the prison intercom, during which his endless stream of streetwise patter amuses both the prisoners and their guards.

In fact, the only person who isn't amused by Greene's gift of gab is Dewey Hughes (Chiwetel Ejiofor), a brother who's at the prison to visit his brother, Milo (Mike Epps), but only because he'd promised their mamma he would. Hughes works at D.C. radio station WOL-AM, where he's just received a demanding new assignment: help turn the floundering R&B broadcaster around.

His big chance comes when Greene, who's just conned his way into ex-conhood, turns up unannounced at WOL seeking a spot in the lineup -- and in the process insulting just about everyone who works there. Hughes balks at first, but eventually gives Greene a chance -- one that appears to end Greene's radio career in a matter of minutes.

But for all their outward differences, Greene has struck a nerve in Hughes' success-hungry psyche, and Hughes decides to give Greene a second chance. To do so, however, he practically has to hijack the station, something that doesn't sit well with Hughes' very white big bossman, E.G. Sonderling (Martin Sheen, looking very happy to be playing someone who's not so obviously liberal).

In classic McHale's Navy style, Greene makes every imaginable miscue on the air, but his ghetto gab brings in more callers than WOL knew existed, and before long Greene is on his way to fame and fortune -- at least for the moment.

But there's much more to Talk to Me than storyline.

There are some incredibly moving scenes, such as the one in which Greene has to announce the assassination of Martin Luther King Jr. Within minutes, the city is ablaze, and people start looking at Greene to do something about it. And he does -- with a little help from, of all people, James Brown.

There are also some -- make that many -- hysterically funny moments, most notably when Watson walks in on Greene, who's, let say, offering an appreciative fan something more than his autograph.

Watson proves herself an effective avenger, and it's not long before Greene is standing before Hughes' door in his birthday suit. It almost turns Talk to Me into a black Odd Couple -- but one inspired by a true story, of course. And the joke doesn't end there: Watson won't let it. Within hours she's exacted her revenge, at the station, with Greene's airtime competition, "Nighthawk" Bob Terry, played with particular relish by Cedric the Entertainer.

Then, too, there's the music, which is both fun to listen to -- "It's a Man's World," "Grazin' in the Grass" -- and timely -- "Time Has Come Today," "I'm Black & I'm Proud." And then there's the everlasting joy of watching people wearing '70s suits and sporting milewide hairdos.

Lemmons, with the aid of screenwriters Michael Genet and Rich Famuyiwa, also offers us an interesting perspective on the late '60s and early '70s, a turbulent time in which the rules -- especially the race rules -- were changing rapidly, and no one knew just which way they were headed. Lemmons keeps the file-footage montages to a merciful minimum, but she makes her point about the period.

Finally, you have a film that's not afraid to say what's on its mind, even when that involves frequent use of the "n" word (always, though, by a black person, usually Greene), and a couple of dozen -- or maybe hundred -- obscenities. This film's not rated R for nothing.

But the truth isn't always pretty, and Talk to Me goes to great lengths to tell the whole story of a man who was thinking just about as far outside the box as you can. At a time when so many films are barely watchable, this one's rewatchable. In fact, I recommend it.