The singer teamed up with pal Ben Harper and his band and hit a low-key studio, where they swore everyone to secrecy.
She tells The Hollywood Reporter, "There was no need for anyone to know. If Sony knew, then they would just be asking where it was, and if Simon (Renshaw), my manager, knew, he would be doing the same thing, so I didn't tell anyone I was even in the studio.
"Ben and his band made that possible as well, because they did it all on spec, and they weren't paid for months. It was cool to have this secret that we all had. Maybe it helped with the bonding.
"I'd say we were seven songs in before I told Simon. But that's a good surprise - to get to say, 'I haven't worked in six years, but I'm seven songs done with an album.'"