Besides music making, teachers must deal with uniforms, tours, candy sales, school funding issues, school administration, and parent organizations. This is a career that is demanding, difficult, and stressful, and consequently there is a great need for good music teachers. Teaching at the university level requires much greater specialization than grade school teaching. The major disciplines are musicology, theory, and pedagogy. There is also applied teaching which I'll describe later.
Musicology is the study of music history.
Musicologists usually specialize in certain areas of history, for example early Russian choral music, or 19th century American composers. Theorists take a scientific approach to discussing music and try to describe the features that make a piece of music good. Music pedagogy is the science of teaching and is concerned with finding how people learn music and how best to teach the subject. And every year many more students graduate with Ph. Ds than there are job openings.