Here is one way to play MP3s from the command line on the Raspberry Pi by using MPG321. This can be installed using:

sudo apt-get -y install mpg321

Once installed we can grab an MP3 to experiment with :

wget http://www.freespecialeffects.co.uk/soundfx/household/bubbling_water_1.mp3

The MP3 file can be played using :

mpg321 bubbling_water_1.mp3

The volume can be adjusted using the ‘g’ command line option. In the example below I set the volume to 50% :

mpg321 -g 50 bubbling_water_1.mp3