'Lost in Translation' director Sofia Coppola and Phoenix lead singer Thomas Mars welcomed a second baby girl, PEOPLE reports. The baby girl, Cosima, was born in New York City sometime "within the past month" according to a source close to the couple.

Cosima is the couple's second child. She joins big sister Romy who is 3½ years old.

The couple confirmed the pregnancy in December when Mars was asked during a backstage interview with Chicago's WXRT if Coppola was pregnant. "I heard the story that if you play Bach, [babies in the womb] get smarter," Thomas said at the time.