Mute when casting to chromecast

App mutes sound fine on Windows volume mixer but sadly doesn't seem to be able to mute sound when it's being cast to chromecast.  i.e. Spotify will mute in mixer but there's no 'casting' volume control there, just able to control volume from spotify app itself I think (which means Ads play sound on chromecast but mute on ok on PC ).  

 Is that possible? 

