1 Touch Response: The keys on a digital piano or keyboard can be weighted (similar to those of a traditional piano), touch sensitive (unweighted but still sound loud when struck hard), or neither.
In very rare instances, eyelid twitching can indicate a more serious condition, like the beginning stages of multiple sclerosis or a lesion on the brain stem. Those conditions typically begin with a host of symptoms, and in this circumstance the eyelid twitch soon moves to the facial muscles, as well.
Causes of eye twitching. Eye twitching, or blepharospasm, is an uncontrollable blinking or spasm of the upper eyelid. Most people develop a minor eyelid twitch at some point in their lives. The causes include: Fatigue; Stress; Caffeine; This minor form of twitch is painless and harmless. It usually goes away on its own. But it can be quite annoying.