How to Change League of Legends Login or Champion Select Music
First of all, I assume that you already have League of Legends installed. I also assume that you have your favorite mp3 file downloaded or kept on your local drive.
C:\Riot Games\League of Legends\RADS\projects\lol_air_client\releases\0.0.1.98\deploy\assets\sounds\ambient
The 0.0.1.98 may be a different number depending on the current up to date release. Choose the highest release number name.
Rename the file to copy its name.
Rename YOUR song as that name. For example, in the video, I chose champion select for blind pick:
I renamed my Woodkid Iron Piano cover as ChmpSlct_BlindPick.mp3
I renamed the original ChmpSlct_BlindPick.mp3 as ChmpSlct_BlindPick(original).mp3 if I am ever nostalgic for the original champion select blind pick music.
Then, log into League of Legends and test out the login or championselect music. It plays!
Woodkid - Iron Piano Cover that I used: