Comment 4 for bug 374059

The problem with using the mpd output in the system mpd daemon is that it will not have permission to speak to your user's pulseaudio daemon.

I have found the easiest way around this is to make a local (to your user) config file for mpd, updating relevant parts of it to point to /home/<you>/.mpd/* instead of /var/lib/mpd/* and having it launch as you on login (I haven't tried launching on startup, but that might work just as well).

Alternatively it is possible to configure pulseaudio to run as a system wide daemon, in which case users (including mpd) need to be in the pulse group (or it might be pulse-access, sorry I can't quite remember), but I have found this can cause other issues with pulseaudio, and isn't recommended by the pulseaudio devs.

For these reasons I don't think configuring mpd to use pulseaudo by default is a good idea, but perhaps someone knows of a better way to set things up, in which case I'd like to know about it ⢁).