Sorry, you are absolutely right.  There are two mpv packages which names
were counter-intuitively swaped.

So `emms-player-mpv` is the one that was integrated in Emms 5.0.
`emms-player-simple-mpv` is the more complete, IPC mpv-based player.

Note that work in being done on the Emms mailing list to integrate the
IPC version, either from the -simple-mpv package or from original work.

--
Pierre Neidhardt

Avoid Quiet and Placid persons unless you are in Need of Sleep.
		-- National Lampoon, "Deteriorata"