It sounds like you have already set up the basic configuration for the Lumin D1 and the PC to communicate via DLNA. To achieve audio output, there are a few additional steps you can take:
Make sure that the Lumin D1 is able to view the shared folder "Music" on the hard drive of the PC. This can usually be done by going into the settings on the Lumin and adding the shared folder as a source.
Check the audio settings on the Lumin to ensure that it is set to output PCM L15 no header. This can usually be found in the audio settings or in the settings for the DLNA server.
Check the audio settings on the PC to ensure that it is set to output PCM L15 no header as well. This can usually be found in the audio settings of the media player you are using.
If you are still having trouble, try using a different media player on the PC to see if that resolves the issue. Some media players may have better compatibility with the Lumin D1 than others.
Lastly, check for any updates to the Lumin D1 and PC software. This could also be a potential solution, as software updates can fix bugs and improve compatibility.
JR should not require any further steps. As long as the Lumin and the PC are able to communicate and the audio settings are correctly configured, JR should be able to access and play the music stored on the PC.