When you type out the command /musicvol (value) in the chat to reduce msuic volume it does not show as a command, and has no option to autofill. Would be nice to have this fixed as you cannot type /mus** and press tab to autofill it.
Excellent news! This has now been fixed by the development team and will be released in a future server update.
Thanks for doing your bit to help us keep the servers bug free!