BTOB's Changsub is the voice behind "Freedom" for the 'Doctor Lawyer' OST.

In the music video, So Ji Sub's character Han Yi Han faces the operation room, and he and Geum Suk Young (played by Lim Soo Hyang) get closer in their relationship. "Freedom" is a ballad about going your own way and finding the light in your life.

Listen to Changsub's "Freedom" above, and let us know what you think in the comments below.