Which branch of musicology primarily studies changes in western art music over time

historical musicology

music theory

systemic musicology

ethnomusicology

The correct answer is A. historical musicology.

This discipline is also called music history. It studies the development of different musical elements through history. For example, it shows how and when the symphony as a musical form has emerged, and how it has changed over the centuries, in accordance with contemporary cultural and artistic trends. It studies the historical contexts, and it will, for example, answer the question why opera was born in the end of the 16th century, and not earlier or later.