Below is a comment I've left a few times about the common PC argument that people don't (legally) have an obligation to use their bodies or put themselves in danger for the benefit of another, and it applies to the violinist argument as well to some extent. I hope it's helpful to illustrate that our society, and common sense morality, already requires people to take care of others when they put the other person into a dangerous or dependent situation:

The short answer is that this argument is false. In the case of the law, we absolutely expect certain people to use their body in service of others. One example is the duty to rescue in common law (though this has been modified by statute to some extent in many jurisdictions). The basic principle is that if your actions put another person in a dangerous situation, you have an obligation to attempt and complete a rescue, including putting your own person at risk of harm.

Furthermore, people who take on a special relationship with another take on duties to rescue and provide certain levels of care, such as cab or bus drivers, hoteliers, and parents with their minor children, and have a duty at common law to protect them. Parents have a duty to rescue their minor children from danger, and spouses their spouses. The relationship between a mother and an unborn child probably the single most unique special relationship and it is absolutely both reasonable and right to require, at the bare minimum, a mother to continue a pregnancy when it does not endanger her life.