After spending Thursday night in the studio, Spears took a break before heading back Friday and working until the early morning hours.
She'll have some famous help with her new disc: At a Louis Vuitton party in New York City on Thursday night, producer Pharrell Williams told PEOPLE he's on board.
Asked about upcoming projects, he said, "The stuff I’m about to do is amazing, but I don’t like talking about what I’m about to do." He paused, then said, "Okay, I’m going in with Britney."
Spears, who filed for divorce from Kevin Federline on Tuesday, has been in New York since last week. On Monday, she made a surprise visit to the Late Show with David Letterman. The following day, she took an ice-skating spin around Rockefeller Center, dined out with friends – and spent hours at the Sony Music Studio.
Complete Britney Coverage
Federline, who performed at Chicago's House of Blues on Wednesday, will be on the road promoting his debut album, Playing with Fire, through Nov. 24. A scheduled Friday-night performance at the House of Blues in Atlantic City was canceled, so instead he'll be in Washington, D.C., for a listening party at the club Platinum. Then it's off to Virginia Beach for a Sunday show, followed by a listening party in Miami on Nov. 17.
At the House of Blues performance, the venue was packed with a standing-room-only audience – though tickets were being given away free.
As for Federline's effort to gain sole custody of his children with Spears, Sean Preston, 1, and Jayden James (born Sept. 12), Sands says, "Kevin's interested in having as much time as he's allowed with the kids, so he wants full legal and physical custody, with visitation rights for Britney." He adds, "If there were no kids involved, it would be easy, but it's going to take time to iron out a lot of different issues."