The University of Indiana's School of Music is the largest college music program in the USA. From their web page, Doctoral Degree Programs:
The Graduate Division of the Jacobs School of Music offers course work leading to the degree of Doctor of Music in the areas of music literature and performance, composition, and conducting. The Jacobs School of Music also offers the Doctor of Music Education degree and, through the University Graduate School, the Doctor of Philosophy degree in the areas of musicology, music education, and music theory.
So a PhD (Doctor of Philosophy) in Music in Musicology, Music Education, or Music Theory would be more oriented toward becoming a person who could teach those particular subjects to undergraduate students in college. These three subjects have to do with academic research and writing books and publishing papers, much more than being a performing musician.
In contrast, a Doctor of Music (DMA) degree would be the highest degree for a performing musician, composer, or orchestra or choral conductor.
I'm not sure what the difference would be in a Doctor of Music Education degree versus a Doctor of Philosophy in Music Education degree.
If you go to the web page above, you can read the requirements for doctoral dissertations for each of the different degree programs, and find links to learn about the curricula.