I've only read the very beginning, but the book [Generalized Musical Intervals and Transformations](https://www.amazon.com/Generalized-Musical-Intervals-Transformations-David/dp/0199759944) by David Lewin was recommended to me by a music professor when he heard I was studying mathematics.  In it, the author analyzes the works of Wagner and others using group theory.

You can find two of his related papers [here](http://repmus.ircam.fr/_media/mamux/documents/lewin-git-1980.pdf) and [here](https://www.jstor.org/stable/843478?seq=1#page_scan_tab_contents).