m-net ~ # /etc/init.d/mpd start
Simple mixer control 'PCM',0
  Capabilities: pvolume pswitch pswitch-joined penum
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 13568
  Mono:
  Front Left: Playback 40 [0%] [10.15dB] [on]
  Front Right: Playback 40 [0%] [10.15dB] [on]
m-net ~ # mpc add /tmp/audio/music/Children.mp3 
error: ACK [50@0] {add} directory or file not found
m-net ~ # ls /tmp/audio/music/Children.mp3 
/tmp/audio/music/Children.mp3
m-net ~ # cat /etc/mpd.conf
music_directory "/tmp/audio/music"
playlist_directory "/tmp/audio/playlists"
db_file "/tmp/audio/database"
pid_file "/tmp/audio/pid"
state_file "/tmp/audio/state"
input {
    plugin "curl"
}
audio_output {
       type            "alsa"
       name            "My ALSA Device"
}
mixer_type "software"

m-net ~ # ls /tmp/audio/music/Children.mp3 
/tmp/audio/music/Children.mp3

m-net ~ # ls -la /tmp/audio/
drwxr-xr-x    4 root     root          140 Jan 14 09:34 .
drwxrwxrwt   18 root     root          660 Jan 14 09:27 ..
-rw-r--r--    1 root     root          270 Jan 14 09:34 database
drwxr-xr-x    2 root     root           60 Jan 14 09:28 music
-rw-r--r--    1 root     root            6 Jan 14 09:34 pid
drwxr-xr-x    2 root     root           40 Jan 13 20:07 playlists
-rw-r--r--    1 root     root          145 Jan 14 09:54 state

m-net ~ # mpc ls
Children.mp3
m-net ~ # mpc update
volume:100%   repeat: off   random: off   single: off   consume: off
m-net ~ # mpc add /tmp/audio/music/Children.mp3 
error: ACK [50@0] {add} directory or file not found