sudo gedit /etc/mpd.conf
Change this line in accordance with your root music folder.
music_directory "/music"
Change the audio output block to use your second sound card. The name field doesn't have to be specific.
audio_output {
type "alsa"
name "USB C-Media"
device "hw:1,0"
format "44100:16:2" # optional
}
Restart MPD so it reads the changes in the configuration file.
sudo /etc/init.d/mpd restart