I wonder why this subject that hasn't been discussed much in a public way on line? In my last google search I was surprised to find only seven entries for "musical code of ethics," and only two for "code of musical ethics." A search for "musical ethics" had many more, but they all seemed to be connected with the business of music, popular or commercial music, or legal ownership of intellectual property. I had hoped to find something addressing musical ethics among practicing classical musicians.
A code of ethics would make life much easier. There isn't really, for example, an established ethical way to deal with situations involving possible performances of new works. Communication between composers and the people they write music for might fall into the category of business ethics, except for the fact that with classical music there is little (if any) money to be made. Ethical situations encountered in teaching music to students might be a lot like ethical situations in other forms of teaching, but they involve issues unique to music.