Those who have discussed the subject of music with myself recently know that I prefer to use the term "theoretical music" (TM) when describing musical functions. Naturally, this phrase is met with slight confusion, as I am currently unaware of its usage anywhere else.
A division of music that uses cognitive processing, mathematics, and aspects of the scientific method to understand and explain musical phenomena.
Along with the simple definition above, theoretical music attempts to examine music from alternate systems and perspectives. For example, approaching certain musical concepts in a mathematical, physical, or even philosophical way can provide new insights. It's not just intellectual comprehension that these multiple perspectives provide. They also present ways to enhance and progress the practical, creative musical landscape. See my post titled M=m for a more in-depth look at how mathematical operations support music, and vice versa.
A theoretical musician studies how music works with a scientific and evidence-based, while at the same time open, mindset. She forms ideas from creative thinking, then tests and validates these theories through reasoning and experimentation. Curiosity is vital, and with the consistent practice of theoretical music, she continually questions and shapes the existing musical understanding found in modern society.
Other terms that deal with explaining musical functions are often rigidly entrenched and settled through years of cultivation and tradition. Theoretical music offers a chance to doodle and muse about the workings of music with a "clean slate," where the ideas therein carry no offense to any establishment. In other words, TM is its own practice with unique skills and interests. Being a theoretical musician is as simple as applying and utilizing the definition above. If these principles already come naturally to you, it is surely already adding to our understanding of how music works. If this is the first time hearing about these ideas, welcome to the world of theoretical music!