By Adam S. Levy - Breaking Celebrity News Staff Writer

Chris Brown's still on probation for beating Rihanna, but in a move that may shock their fans, the pair are making music once again.

The Barbadian beauty and volatile vocalist have collaborated on two remixed singles -- of her song Birthday Cake and his Turn Up the Music --  just three years after he brutally beat her following a pre-Grammy party in Hancock Park, a suburb of Los Angeles.

Listen To Rihanna & Chris Brown's New Single (WARNING: Explicit Lyrics)

Brown's first line in Birthday Cake?

"Girl I wanna f*** you right now. Been a long time, I've been missing your body," the Grammy-winning R&B hit-maker sings.

Meanwhile, Rihanna tweeted a link to Turn Up the Music late Monday.

As we previously reported, Brown, 22, tweeted "HAPPY BIRTHDA