When she started preparing for the National Geographic series “Genius: Aretha,” the showrunner Suzan-Lori Parks did what one often does before tackling a biographical project: She crammed. Her approach was a little unusual, though.

“I spent months and months reading about what she said, and also noting what she didn’t say,” Parks said of the singer, songwriter and activist Aretha Franklin in a video conversation last month. “Jazz musicians will remind us that the music isn’t just the notes, it’s the stuff between the notes, the silences.”

And there were plenty of both during Franklin’s extraordinary life — the focus of the third season of “Genius,” which premieres on March 21 with the British actress and singer Cynthia Erivo in the title role. For Parks, that presented both an opportunity and a challenge: Franklin tried hard to control her public persona, which didn’t seem to be a huge priority for the subjects of the two previous seasons of “Genius,” Albert Einstein and Pablo Picasso, whose sometimes less-than-stellar behavior might have even enhanced their mystique.

But for Franklin, a Black woman who rose to superstardom amid the Civil Rights conflagrations of the 1960s, the stakes were different.

“I think she very much wanted to be seen in a certain way,” said Parks. “As Black American people, we are very aware of our marketability, and as Black American artists, we are maybe even more aware of our marketability.”

“My challenge,” she added, “was: ‘How do I tell the truth about this Black American woman who is a brilliant icon? And how do I tell the truth and be respectful?’”