STOCKHOLM — When Karin Dreijer, half of the Swedish electronic duo the Knife, first emerged in her solo guise, Fever Ray, the words most often used to describe her music and live shows were chilly: glacial, mysterious, claustrophobic. “Fun” was rarely one of them.

So finding out that fun should be the defining feature of her second album, “Plunge,” was almost as much of a surprise as the existence of the record itself — it dropped, unannounced, in October. It’s been supplemented by a series of videos featuring Ms. Dreijer engaged in a sadomasochistic tea party and battling relationship demons: a story that may continue in the live tour she begins this month.

The album still features the dense, velvety layered textures of her debut, with brighter, clearer vocals. But there is one major change: She’s singing about sex. A lot.

“I think it’s very weird as an artist to stay in a certain atmosphere for your whole life,” Ms. Dreijer said over coffee on a subzero day here. And in the eight years between albums, she has undergone significant personal shifts, starting with a divorce from her husband. But “Plunge” is no breakup record. Instead, it investigates and celebrates what it means to be single, what it means to be free.