First of all, in this analogy you in no way caused the violinist to hook up to you. This attachment occurred against your will and "the society of music lovers" has in this case severely violated your rights. I would like to demonstrate in this post, however, how the common moral intuition in this case fails when scrutinized logically.
As I see it, the main reasons many people see unplugging the violinist as acceptable are twofold.
Firstly, being attached to the violinist is a huge pain in the neck. You need to stay in bed until the violinist recovers. I doubt many people would have the same sense of outrage if you could more or less go about your business. However, as I demonstrated yesterday, the right to life supersedes the right to liberty. Just like the intention of act of causing the avalanche, the intention of act of unplugging yourself is to regain your liberty and to "undo" the situation you have been unjustly placed in to.
The objection based on positive and negative rights will be addressed in the next section.
Secondly, the situation they are placed in is incredibly unjust, and unplugging is seen as merely returning to the situation prior your kidnapping in which the violinist was dieing of natural causes and you had no greater moral obligation towards him than towards a man on the other side of the planet. However, regardless of how this situation came to pass, we need to consider the present situation.
I will grant that the violinist lacks the positive right to life: the right to use your body; if you could unplug yourself without killing the violinist, I doubt anyone would object. Also, if the violinist were to approach you and demand your assistance, I would be the first to say that you have no obligation to come to his aid; this represents a situation in which you are passively letting the violinist die.
However, in the present situation, you are already hooked up to the violinist. As such, you cannot disconnect yourself because the violinist's death would be a direct result of your action; this is a situation in which you are actively killing the violinist. Because of this fact, the violinist's negative right to life comes into play, just as in the avalanche scenario. Regardless of how this situation came to pass, even though the violinist has no right to your body, your moral obligation to not kill (cause the death of) him takes over.
I may seem like I'm repeating myself, but I want to make sure I have made my point in a way everyone can understand. It may seem counterintuitive that the society of music lovers could impart upon you an obligation that you didn't previously have, or impart upon the violinist a positive right he never had, but the point I'm trying to make is that the application of negative rights is more than adequate to show why unplugging yourself is wrong. Positive rights apply to inaction while negative rights apply to action. Many see the act of unplugging as merely choosing not to allow the violinist usage of your body, but that choice has already been made (I'm sure we can all agree that the society of music lovers have violated your rights).
Because unplugging the violinist is not an act of inaction, the violinist's negative right to live comes into play, and as such, it is immoral to unplug yourself.
However, because your intent was not to cause the violinist's death, in the current legal system of the United States would most likely charge you with manslaughter and not murder. In addition, if the violinist chose to be plugged in, unplugging would be justified as self-defense.
To sum up, while you have no moral obligation to remain plugged in, you do have an obligation not to act in such a way that said action leads to the death of an innocent human being.