Primary and Park Myung Soo worked on music together.

Yesterday, Primary posted on her Twitter, "Working with Myung soo Oho" along with a picture.

The picture is Sylvester Stallone holding up both of his thumbs in a movie scene, reveaing the satisfied heart of Primary while working with Park Myung Soo.

The two are working on music as partners for the music competition being held in MBC "Infinite Challenge."

Photo Credit: Primary Twitter