I use the rear speakers and center when I listen to classical multi channel music. Some that are recorded well are fabulous. Some not so much. It depends on whether the recording was actually made that way.
Who Uses Rear Surround Speakers For Music Playback?
I feel a very slight surround fill improves music playback. Similar to a subwoofer I set it low enough that you can't point to the sound source. I've found the smallest/affordable speakers in the rear are able to make a noticeable difference. What is your opinion on this subject?