Three .js object rotation on keypress

I'm desperate. been trying for so long to simply rotate an object on key press event. I can't just figure it, can anyone please show how to do it?

this is my model http://ift.tt/1HjqCTP

i need to keep rotating it on x axis, as long as keyboard button "B" is pressed down, so that that the shadow from the spotlight or direct light would be changing. anyone?

i need to do that with the whole alphabet (i've got all the models) what's the best way to do it?