Lets say you are a young, adult female violinist who decides to take classes of violin. Just for this illustrative case, lets say you decide to try out a male teacher that is between 2-20 years older than you. What kind of exercises and elements in the teaching could be considered as appropriate, and what would you not consider as being totally OK? What are the red warning signs? What would you, as a teacher, not do on your student? (Even if might be helpful for the purpose of violin playing, but not to make it her/him feel uncomfortable?)