worked (for yt) . . . doesnt mean its not a bit sus tho

(2020-09-25) Just used it on soundcloud. It works :)

Very useful addon. Along with this simple ahk script it works in non-focused browser window

#IfWinExist ahk_class MozillaWindowClass
Media_Play_Pause::ControlSend,, {Media_Play_Pause},

goooooooood

Works perfectly on MacOS, just make sure you set up the shortcuts.

Thanks for the update! Is there a chance to include the mixcloud handler?