Well, it seems that was the problem... Thank you! Sorry for the newb question, but how could I see if a knob is assigned to control something? I did it in a workaround way I think - I just assigned the knob to do something (I suppose it overwrites a previous assignment if there's any), then I deleted that new assignment and voilà! - the knob is obviously available and I could assign it to the tempo fader. But as I tried before that to assign every single knob on my keyboard and none of them worked, it means all of them are assigned to something (right?)... so... is there a way in Logic to see what the knob X actualy does?