You need to configure this inside VLC: Tools > Preferences > Hotkeys then click under "Global" and press hotkey combination.
BTW, in my opinion VLC isn't the best choice for music, it's a bit heavy on resources for music and when you play\pause it takes him a few seconds to fully stop. I use Foobar 2000 (after trying several other music players), it's very light on resources (though I've seen others even lighter) and it has many available plugins.