Change settings on other applications while playing League (closing windows, pausing videos, etc.)

So occasionally while I'm playing League I end up leaving some music playing in the background or something, and while playing I end up having to turn it off beacuse it interferes with my game (FPS drop, higher ping, audio interruptions). But whenever I try to hide the League window to change those settings the Hide shortcut (Cmd + H) doesn't work, and trying to close running applications through the Force Quit menu ends up crashing League. Anyone know if these bugs can be solved? Thanks!

Edit: Any workarounds would be nice too. [garen-swing]