(FORTUNE Magazine) -- When Danny Bennett began managing his father's career in 1979, Tony's music was out of fashion and the singer was without a recording contract. In the decades since, Danny, now 52, has helped his dad conquer the MTV (and iTunes) crowd and cement his status as a living legend--who still makes hits. (He also has a thriving side career as a painter.) With Tony celebrating his 80th birthday, FORTUNE's Corey Hajim visited the Bennetts' downtown New York office to find out how father and son work in harmony.

DANNY: It's been said that Tony never sings the same thing more than once because of his style. That kind of describes how we work: There is no typical day. There is no 9 to 5. The business and personal are fluid. I call him "Tony" professionally. I would never make a presentation at Sony and say "my dad." It's not a good negotiating position.

TONY: I am in a perpetual state of learning, and Danny takes care of all the superfluous details. That gives me the freedom to concentrate that I've waited about 40 years for. It's wonderful.

DANNY: I am an e-mail freak. Tony likes to speak by phone. Ideally, we prefer to speak face to face. There are certain things I can do because I know him so well, but he signs off on everything. I like to put things together so it's very concise and the artist can do what he needs to do. He loves to tour, but he doesn't tour like the Rolling Stones--out for two years. It's more like six or seven dates a month.

TONY: Danny set it up so that I have about 25 days per month where I am free to paint. I don't feel like I need a vacation to get away from it all. I just like what I am doing.

DANNY: His big conflicts came when the Sinatra kind of music faded out and rock & roll took over. The marketing guys said, "You gotta wear love beads and sing 'big wheels turning,' " or whatever it was. Tony can't do that. It's not toothpaste--put it in a tube, color it red, or put sparkles in it. You can't do that with artists. It is his integrity that sells. I made a promise to Tony that he can make the great music, and I'll just come up with marketing that fits what he does. Tony's MTV Unplugged is his bestselling album ever. I knew if he got in front of 18- to 20-year-olds, they'd love him, because they'd feel his energy. It's about selling Tony as an American icon. I'm not dealing with a career, I am dealing with a legacy.