Kdramas With Bewitching Music (Actually Played in the Drama)

This is a list of Kdramas with wonderful Osts that were actually played in the drama. I notice that many dramas have enchanting Osts, yet they are only played once or never during the drama. 

One example is Nobody Knows. It had such a haunting song that perfectly suited its story and theme, yet it was only played once or twice in the first few episodes. There were so many scenes where I was waiting for it, but nope, no... 

Another example would be Vincenzo. Damn the Ost was fire! Yet....

I dont know if it's the same with everyone else, but even if I dont like the story or some characters, but the music is good, then I end up watching the drama for that. 

This is not a list of Kdramas with good music. It is a list of Kdramas with Osts that (according to me) make use of that good music and play it at the right moments. Watch if you are the kind of person who watches Kdramas partially for the music.