Chris Brown rapped a new un-released song alongside Rihanna while at a party for P.Diddy earlier this week.

While at Supperclub in Hollywood Wednesday night, Brown rapped in front of an audience that included artists Ne-Yo, Red Café, and more.

Though Rihanna did not sing during the impromptu performance, the two are working on their second single together, a spokeperson for Brown confirmed to E! News last month.

There is no hint as to what the song will be about, but based on previous songs they have worked on collaboratively; it will likely be about their unique relationship.

Brown already collaborated with Rihanna for the song, "Nobodies Business," which is featured on her seventh studio album, "Unapologetic."

Previously, they worked on the hit single, "Umbrella," together, then remixed each other’s singles, Rihanna’s "Birthday Cake," and Brown’s "Turn Up The Music."

The pair caused controversy when she featured him on the remix of "Birthday Cake," since on the track, Brown sings, "Girl I wanna [expletive] you right now. Been a long time. I’ve been missing your body. Let me turn the lights down. When the window go down, it's a private party."

Rihanna also sang on his song, "Turn Up the Music," saying, “"Turn up the music cause I feel a little turned on/ Turn on the music, don't you try to turn me down." She later says, “I love you baby.”

Back in 2009, Brown infamously assaulted Rihanna, hitting her so forcefully that she had major contusions on her face, a split lip, and a bloody nose.

Brown eventually pleaded guilty to assaulting Rihanna and was ordered to stay away from her until 2011.

Since then, they had rekindled their romance.

To contact the editor, e-mail: