Bob Dylan's been making music since the '60s, but biographers still don't seem to be any closer to capturing the private side of the enigmatic pop icon.

Next Sunday's two-hour A&E Biography (Aug. 13, 8 pm/ET) of Dylan ? the latest attempt at revealing what makes the singer tick ? adds little to the previous profiles on the singer-songwriter. But it might just be that fans are looking for complexity where it doesn't exist, offers fellow musician Cesar Diaz.

"He's a very simple man," says Diaz, who's toured with Dylan in recent years. "He doesn't like to be called Mr. Dylan or [his real family name] Mr. Zimmerman. He just likes to be called Bob. He likes to melt into the background and be left alone, and I think that he hates the day that he made it."

So what compels the 59-year-old Grammy winner and Rock and Roll Hall of Fame honoree to continue touring? "He likes to be out there because he likes to feel young," Diaz continues, "and [know] that he can still do it."

Even going back to Dylan's early days as a struggling folk singer in New York's Greenwich Village, colleagues tried in vain to get a peek behind the curtain that enshrouded him. Says fellow '60s folk singer Dave Van Ronk: "There was always a core of Bobby that nobody could reach."

Journalist Al Aronowitz, meanwhile, has his own take on the music legend: "Bob is one of the most charming men I've ever met," he says. "[But] he can be the meanest bastard."