(FORTUNE Magazine) – Tom Joyner is the most influential radio personality that most white folks have never heard. Reaching one in four African Americans, his show is becoming a must-buy for sponsors, some of whom support his philanthropy. Procter & Gamble backs Take a Loved One to the Doctor Day, and GM is behind his voter-registration drives. His media company, Reach, has just extended its grasp, with a syndicated TV variety show that kicked off this fall. Joyner, 56, was recently in New York to be inducted into the Broadcasting & Cable Hall of Fame (other honorees included Ted Koppel and Oprah Winfrey). He talked with FORTUNE's Cora Daniels about what it's like to be, as he's known, the "hardest-working man in radio."

More than eight million listeners in 115 markets tune in to your show each morning. Yet much of America isn't familiar with you. Please introduce yourself. If FORTUNE readers don't know who we are, that's fine with me, because we specialize in and superserve the African-American audience, which is an underserved market. I am Tom Joyner, and I'm a DJ with a biiiiiiig microphone.

Should corporate America directly target black consumers? The African-American market has a lot of disposable income. When you show us that you want our business, and you are willing to help us be stronger and a better community, that means something. We have been able to show advertisers that our audience will be brand loyal ... [dramatic pause] forever.

You have often said you have no desire for crossover. Why? I am always surprised when people who don't look like my audience say they listen to [my show]. I don't go after it, but I'll get it anyway. They are coming because they want to hear or be a part of this experience of being black, not to see how crossover I can be. You should be true to your audience.

With all the buzz about satellite radio, do you worry that traditional radio is dying? Yeah, I'm worried. There are so many other places for people to get entertained and informed now. Radio has to be more involved in the market that it serves. Going back to the civil rights days, how did Dr. King tell people in Montgomery to boycott the buses? That happened on radio. And that is what black radio, particularly, was all about. If radio in general, and particularly black radio, is going to be viable, we have to do those kinds of things. Those are the kinds of things we do on our show--for instance, the way we became a forum for the community in the aftermath of Hurricane Katrina.

Now you're in the Broadcasters Hall of Fame. Let's not talk about that. I don't think I'm old enough for any of that lifetime- achievement stuff yet. I hope not.