Dave Grohl — the Nirvana drummer and Foo Fighters founder — is as close as America gets to a rock ’n’ roll father figure: funny and family-oriented, beloved by his fans and his fellow musicians and seemingly as steady as the drumbeats that made him famous. His nickname? “The nicest dude in rock.”

On Tuesday, however, that reputation took a hit when Mr. Grohl revealed that he was also paternal in a very real, and decidedly less flattering way, with the announcement of the birth of a daughter outside his marriage.

“I plan to be a loving and supportive parent to her,” the musician posted on Instagram, adding that he loved his wife and their children. “I am doing everything I can to regain their trust and earn their forgiveness.”

The decision by Mr. Grohl to make a pre-emptive announcement may well have been an attempt to control the narrative, something that crisis communications experts said was savvy.

“I thought it was clean, smart, simple,” said Melissa Nathan, the chief executive of The Agency Group PR, which specializes in “reputation management.”

Molly McPherson, a crisis communications strategist, echoed that sentiment, saying that Mr. Grohl’s post was probably strategically timed, coming on the same day as the highly anticipated debate between Vice President Kamala Harris and former President Donald J. Trump.