Can {Disdainful Stroke} counter a {Chord of Calling} if X is at least 1?
202.3b (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=202.3b): When calculating the converted mana cost of an object with an {X} in its mana cost, X is treated as 0 while the object is not on the stack, and X is treated as the number chosen for it while the object is on the stack.
That means if x>1 you can.
Yes 1 or more