$ m volume help
usage: m volume [ level(0-100) | change(-n|+n) | up | down | mute | unmute | ismute ]
Examples:
m volume 70 # set the volume to 70 %
m volume +5 # increase the volume by 5 (up to 100)
m volume -10 # decrease the volume by 5 (down to 0)
m volume up # increase the volume by 6.25
m volume down # decrease the volume by 6.25
m volume # get the volume level
m volume mute # set mute
m volume unmute # unset mute