K-Pop Kollaboration is an occasional column presenting the latest news about who Hallyu artists are working with.

There's no denying that the scheduled duo performance from Lee Hyori and 2NE1 rapper CL at the annual Seoul Broadcasting System (SBS) Gayo Daejun music festival in Goyang on Sunday is the most anticipated collaboration in K-pop right now.

According to one SBS spokesperson, the pair has been working overtime preparing for their high-profile collaboration.

"Apart from talking on the phone, [Lee Hyori and CL] are even holding meetings behind closed doors to work on their collaboration," the spokesperson said.

Lee, who was married to Rollercoaster guitarist Lee Sang Soon back in September, has been on an extended honeymoon on Korea's Jeju Island.

According to a press release published Monday by CL's record label YG Entertainment, the former Fin.K.L has been commuting between Seoul and the island vacation destination.

"All eyes from South Korea and abroad are on the two most powerful divas of the South Korean pop music for the upcoming, unprecedented performance," the release added.

The Gayo Daejun performance will reportedly feature new versions of Hyori's "Bad Girls" and CL's solo single "The Baddest Female," remixed by YG Entertainment's in-house producer Teddy.

The appearance at the annual music festival will mark Lee Hyori's dramatic return to the stage, in her first concert as a married woman.

"This is the first time the two will be showcasing a performance together," last week's YG announcement of the performance read.

Even before their closed-door meetings, the two K-pop superstars had reportedly been speaking frequently to discuss their upcoming performance.

"Lee Hyori and CL are contacting each other on the phone often to discuss what they will be showing [the crowd] at the 2013 SBS 'Gayo Daejun,'" the record label release read.

The collaboration reportedly grew from a conversation the two artists had at an after-party for this year's Mnet Asian Music Awards in Hong Kong.

CL and Lee have reportedly become quite close in the process.

"The two have shown great affection for each other," the label's statement read. "Such friendship played a big role in making the upcoming collaboration happen.