Sound via Command Line
mpd is a music playing daemon [mpd.wikia.com], this means its a server side service that runs on your RPi in the background. mpd builds and maintains a database of all your music so you can access it with a client for anywhere on our network.
Once properly configured mpd can be controlled via the command line utilities using a client tool such as mpc  or a console client like ncmpcpp. Graphical clients also exist.
sudo apt-get install mpd mpc ncmpcpp
This command will install the tools we need and automatically resolve a stack of dependencies. On my system it took about 10m to install everything.
By default the mpd install creates a conf file for you owned by user 'mpd' in group 'audio'.
sudo ls -all /etc/mpd.conf
-rw-r----- 1 mpd audio 12240 Jun 2 22:48 /etc/mpd.conf
Check that your user is in the 'audio' group using
cat /etc/group | grep audio
On my system this gave, which didn't have my user
If necessary add yourself to the group using;
sudo usermod -G audio <username>
With the correct permissions the audio group can read the conf file, therefore its still necessary to use root to modify it.
Modify the mpd config to point to your music folder
sudo nano /etc/mpd.conf
find the line that begins
music_directory "~/music" and alter the location in "".
mpd runs as a service so to initialise using the new config use
sudo service mpd restart
Update the Database
mpd should be running and the best way to update the database is to use the client mpc,
Updating DB (#1) ... volume: 86% repeat: on random: on single: off consume: off
this may take a minute or two depending on how much music is parsed.
Loading a playlist to mpd
Navigating the database and selecting track for a playlist needs a client like ncmpcpp. Lauunch the utility using
Press '1' to get the command menu. Basically, press 'space' to add a file or folder to the playlist.
I've not found a way of saving a playlist.
When you quit ncmpcpp, mpd will continue playing.
sudo mpd --kill
- mpd seems to reload the current playlist and start playing it automatically on RPi restart.
- sudo privs are needed to kill playback. This is because of permissions.
mpd --kill config: problems opening file /etc/mpd.conf for reading: Permission denied Aborted