How do I adjust login screen music volume?

So i'm using a custom login screen, but the problem with that is the volume is extremely low. When I play the file on it's own (SWF file), the volume sounds fine. But when the league login screen opens, it plays half as loud. My volume mixer is even on all applications. Does anyone know how to adjust the volume of the login screen or atleast somehow make it not play so quietly? Thanks!

EDIT: Oh I found out you could adjust on the game menu (non ingame). However this changes my champion select volume as well, is there any way to just change login screen volume?