It was a noteworthy week for kdrama soundtracks, with miss A's Suzy adding a song to the OST for "Gu Family Book" and JYJ's Junsu contributing to the soundtrack for "Heaven's Order."

Suzy, also the lead actress in "Gu Family Book," performs "Don't Forget Me," the love theme for her character Dam Yeo Wol. The lyrical ballad describes the character's love for Choi Kang Chi, played by Lee Seung Gi. In the drama, a wise man tells Dam Yeo Wol to avoid anyone she meets by a flowering tree, under a crescent moon. But Yeo Wol sees Kang Chi there and cannot help but fall for him even though he is at best only half human.

Kim Sun Min, who wrote "Cocktail Love," composed the simple yet evocative melody. As soon as the song was released, the track ranked high on different online music charts. The surge in popularity was partly due to Suzy's fan base and partly due to the drama, which has led viewer ratings or weeks now. It's not the first time Suzy has contributed to a drama soundtrack as she also sang on the OSTs for "Big" and "Dream High."

And if Suzy's song made it a good week for soundtracks, Junsu made it an even better one. The viewer ratings for this week's showing of "Heaven's Order" were higher than last week's, and one reason may be Junsu's appearance during the broadcast. The JYJ singer performed the song "Stupid Heart." Although C-JeS Entertainment had not planned to release the song so early in the drama's broadcast, it seemed a timely match with developments in the love story between Won, played by Lee Dong Wook, and Da In, played by Song Ji Hyo.

A representative from the "Heaven's Order" drama production company said that Junsu's song would help viewers relate to the love story because, "As a skilled vocalist, Kim Junsu was able to express the ardent love story with overflowing emotion."

Not only did the drama place first in ratings the day the song was released, keywords relating to the song immediately started trending on search charts.

Junsu has been watching the show and was happy to do his part in boosting ratings.

"I am enjoying watching "Heaven's Order," said Junsu. "I hope my singing can convey the emotions expressed by the lead actors. I tried to deliver the sad and earnest lyrics as sincerely as I could."

The song, "Stupid Heart," will be available on May 15 on online music sites. Junsu also contributed to the soundtrack for "Scent of a Woman."