Use of Login Screen Music

So, I'm coming back to league after several years of not playing it and upon my return, I was reminded of the wonderful champion login screen music. In the time since I used to play, I took up ballroom dancing and quite recently I've enjoyed recording demonstrations every month or two and posting them on YouTube. Thus far I've used songs by producers on YouTube who are small enough to get a hold of directly and ask their permission. How would one go about that process for login music? Is it copyrighted, and if so, what channels do I go through to get the proper releases and permissions? Any help would be greatly appreciated.