What do you call the scientific study of insects?
That's an easy question to answer - it's "entomology".
With music the question is not so straightforward to answer.
The most unambiguous term to describe the scientific study of music is "Music Science".
But often people use other terms to describe activities that count more-or-less as scientific research into music. Including:
Musicology
Music Perception
Music Cognition
Music Psychology
Biomusicology
Philosophy of Music
Musicology
Wikipedia tells us that "Musicology" is:
the scholarly analysis and research-based study of music.
In principle this definition includes all of music science. But it also includes anything that is "scholarly" but not necessarily "scientific". I would dare to suggest that "musicology" in practice is used to describe studies that are mostly not particularly scientific in nature.
If you're doing music science, and you want people who are looking for music science to find your music science, you probably don't want to call it "musicology", because then your research would be lost in a sea of non-scientific "musicology", which no one is looking for.
Music Perception and Music Cognition
"Music Perception" and "Music Cognition" are two similar terms. They both imply something about music, ie that music is something to be perceived or understood ("understood", because "cognition" doesn't have a verb in English).
There is no doubt that music listeners respond to music in various ways. But it is not at all certain that those responses count as the actual perception or understanding of something.
Both of these phrases are popular as categories for describing some types of scientific research into music, but, the problem for me is that they come loaded with this implication that "perception" and "cognition" are meaningful terms when applied to music.
Music Psychology
"Psychology" is defined in Wikipedia as:
the scientific study of mind and behavior in humans and non-humans
Given that music is something that only exists because of the effect it has on the mind of the listener, it could be argued that "Music Psychology" encompasses everything that could be considered "Music Science".
But, Wikipedia tells us further that:
It aims to explain and understand musical behaviour and experience, including the processes through which music is perceived, created, responded to, and incorporated into everyday life. Modern music psychology is primarily empirical; its knowledge tends to advance on the basis of interpretations of data collected by systematic observation of and interaction with human participants.
To me this implies that Music Psychology is more limited in its scope, and it does not necessarily include everything that might count as Music Science.
Biomusicology
“Biomusicology” is a term invented by Nils L. Wallin in 1991, which attempts to bring together all the biological aspects of the study of music. If we take the view that Music Science is actually a sub-field of Biology, given that creating and listening to music is a human activity, and humans are living organisms, then "Biomusicology" is very close to just being a synonym for "Music Science".
Music Theory
"Music Theory" sounds like something that might be scientific. After all science is all about finding theories to explain stuff.
"Music Theory" mostly refers to the systematic description of specific features of music, and also how those features should be notated.
Of course science often starts with systematic description of the thing being studied, so the content of Music Theory is highly relevant to Music Science, even though Music Theory is not itself an actual scientific "theory" about music.
Philosophy of Music
"Philosophy" seems like something distinct from science, and historically Philosophy was something that happened before proper modern Science was invented, and Philosophers would just sit around thinking about the nature of reality, instead of going out and doing actual observation and experimentation.
Wikipedia defines the "Philosophy of Music" as:
the study of "fundamental questions about the nature of music and our experience of it".
A good introduction to the Philosophy of Music is the Stanford Philosophy of Music page.
Here are some things that "Philosophers" of Music think about:
Should we study "Pure" music, or should we study all music?
The idea is that "Pure" Music is uncontaminated by other non-musical things like words. Of course if it turns out that music and words are intimately related in their evolutionary history, then deciding never to study "impure" songs with lyrics in them might be a bad idea.
What is the Definition of Music?
One can take the view that any definition we have of music isn't very good, precisely because we don't scientifically understand what music is.
Is a "musical work" a mental entity? Or is it just the performances of music that actually exist?
I feel that this is one of those questions so silly that only philosophers would find it necessary to over-exert themselves trying to answer the question.
“For instance, is the use of a harpsichord required to instance Bach’s Brandenburg Concerto No. 5 in performance? Would producing harpsichord-like sounds on a synthesizer do just as well?”
Even sillier. Like maybe it would, or maybe it wouldn't. Presumably it might depend on which synthesizer sound was used instead of the "real" harpsichord. Maybe some sound completely different to a harpsichord would give a better result. Have these guys not heard of the "remake"?
How can music express emotion?
In as much as music expresses something that is identified as emotion, this is a question that ultimately can only be answered by a scientific understanding of how and why the listener's brain responds to music the way it does, possibly supplemented by a better scientific understanding of how the brain represents and processes emotions, or conversely, what emotions actually represent.
Some philosophers seem to expect that there should be some logical relationship between what music is and how it can express emotion. But there is no particular reason why this should be the case.
How can one "understand" music?
Maybe music is not something that can be "understood". The listener’s brain responds to music in certain ways, and that’s it.
Where does that leave us?
In practice all these terms used to describe research into music are in competition with each other. If you are doing some kind of scientific research into music, be it theoretical or practical, and you have to choose a label to describe what it is that you are doing, then you have all those choices to choose from. You may care about framing your research in a way that clarifies the scientific nature of your research, and call it "Music Science" or "Biomusicology". Or, you might call it one of "Music Perception" or "Music Cognition", because you know that those are the labels that have historically been used for the type of research that you are doing.
Appendix: Sub-reddits
If you want to discuss some aspect of Music Science on Reddit, then (usually) you want to choose a sub-reddit to post it to.
So how many of the terms listed above have corresponding sub-reddits?
I found the following:
That's 5 out of 8. Missing from the list of terms covered in this article are:
Music Science
Music Perception
Biomusicology