Just fyi, the reason controlling the volume of each ear independantly on DJ headphones is of interest is because when you mix music (called beatmatching), you listen to the track playing (through your booth monitors generally) and the track you are queing (through your headphones), match their speeds/pitch, then you manipulate the vinyl (or cd, or whatever you use) by brushing your hands to slow it down or giving it a nudge to speed it up until they are syned.
That said, deep deep bass really isn't that important in a DJ headphone, because really you match the drums. But, for mom it would be cool.
Anyways, random, back to mothersday....
My sister and I got my mom a manicure and facial (sister made appointment, I paid.... heh)