SS501's Heo Young Saeng has just released an OST track for SBS drama 'Protect the Boss' entitled "Sad Song." The track, comprised of a gentle guitar and piano melody, is perfect for a late summer night. It was written specifically for the love story between No Eun Sul (played by actress Choi Kang Hee) and Cha Ji Hun (Ji Sung) and is aptly very emotional. Composed by Jun Hae Sung who also created OST tracks for 'Secret Garden' and 'The Greatest Love,' the song fits both the drama and Heo Young Saeng's voice perfectly and has already won the praise of the actors. Heo Young Saeng has previously done solo OSTs for SBS 'Will It Snow on Christmas' and 'I Love you.. I'm Sorry..', MBC 'Our Legend of Friends' and 'Erasing Tears' as well as with group SS501 for SBS 'Internal Doctor Bong Dal Hee,' 'Childhood Memories,' 'Love I Can't Forget,' KBS 'Boys Over Flowers,' 'Because I'm Dumb,' and 'Making A Lover.' Other singers who have worked on the drama's OST include JYJ's Kim Jae Joong, Lyn, M Street, A Pink, Kwang Hee of ZE:A, and Ye Won of Jewelry with tracks titled respectively, "I'll Protect You," "You Don't Even Know," "I'm Asking," "Let Us Just Love," and "I Only See You." The OST tracks have all been well received by the viewers. Heo Young Saeng's newest addition to the OST is now available for purchase on Soribada, Bugs Music, Cyworld, Dosirak, MNet, Naver music, Daum music and other music sites as well. The OST album will be released on September 9th. Source & Photo: X Sports via Nate