Sofia Coppola, Thomas Mars Sofia Coppola, Thomas Mars

Sofia Coppola and her longtime boyfriend, Thomas Mars of the band Phoenix, are expecting their second child, he confirmed.

See photos of Coppola

"I heard the story that if you play Bach, [babies in the womb] get smarter," Mars told Chicago's WXRT, adding that he probably won't play tunes from Phoenix's new album, Wolfgang Amadeus Phoenix, for the baby. "We have to study it."

Watch clips from Lost in Translation and Marie Antoinette

Coppola, 38, and Mars, who have been together for four years, are already parents to daughter Romy, 3. The Oscar-winning screenwriter and director's next film, Somewhere, will be released next year.