I can of course, send files to any network device, but then I have no visual of the progression , or any means to forward, skip, pause etc...
On the server PC, you have two ways to see and control a remote renderer:
1) Left Click on the renderer itself under Playing Now. That opens a view tab which displays the renderer's playlist and gives you full control over it. Select music from other tabs and it should be added to renderer's playlist here. This should be essentially the same as Player for a local renderer - you can even display lyrics, etc. (You may run into a recent issue where the album cover art sometimes does not show up.)
2) Click on Overview under Playing Now. That opens a view tab showing playlists for all remote renderers visible on the network. Select one and add music selected from library views. Right mouse button click on any track for a long menu of controls. You can even drag and drop tracks between remotes, etc.
The usual Player Controls in upper left corner of the MC window also work for a remote when its tab is selected.
These work well for my audio files. Do they not work when sending stuff (?) to your HT?
