The academic discipline of music is split up into several different areas that basically anyone studying music has to have some degree of knowledge and skill in, but will choose to focus on one or a few of them. These include, generically:
Performance
Theory
History/Musicology
Pedagogy
Not surprisingly, if your focus is performance, you focus on performing. That usually entails taking more ensembles than if you were focusing in other areas. These vary in most academic settings from orchestral performance of your instrument (such as playing in a university orchestra), chamber playing (brass quintets, trombone ensembles, etc.), or even more exotic or secondary types of music such as "world music", pop music production, piano, jazz, baroque/period instrument performance etc. I include jazz in this list because some universities put popular and jazz idioms as a secondary skill of an instrument. However, many universities allow you to specialize in these areas (jazz, performance of period instruments etc.) So your experience in the "performance" side of thing is going to vary from university to university. Some undergraduate programs (and masters I just learned!!!) require performance majors to play in their school's marching band!!
Pedagogy is another big area that gets a lot of attention because its how many people put food on the table. There is also a legal apparatus in the US and throughout many other parts of the world that require you to have a license to teach music at public institutions so these can be rigidly defined depending on what types of certifications will ultimately be granted. As such, there might be many requirements --- in my school I had to learn string, woodwind, bass, percussion, and guitar as well as elementary music curriculum planning and chorus. That's a lot of classes to take. I believe it was 150 credit hours (incidentally the same as accountants to become a CPA!).
In my personal experience, the performance degree was basically the education degree minus most of the education classes. The replacement for these to maintain academic standing was to increase the number of requirements for performance (again, not surprising!) as well as substitute a single pedagogy class focused on your instrument and building a private studio. The remainder of the balance could be filled in anyway you liked and now there are minors you can add to them as well that also fill the gap for your major requirements at that university. So you could pick up a secondary specialty in musicology, for example.
All of these majors have a theory expectation, this is usually segmented into three subcategories:
Aural
Written
Piano
Some permutation of these exists in every music school I've seen, though many put piano as a sub requirement of, say, written instead of having separate classes. The idea with Aural theory is that you can identify how to perform and interpret music based on what you hear. This can include dictation but also singing apporpriate intervals unassisted and the like.
Written theory starts with Bach, more or less. Using this "functional harmony" as a basis, you write chorales and learn how functional harmony works, then you progressively "break" it the further in the process you get to. Performance majors don't get much beyond counterpoint if you don't want to go any further. However, you also cover analysis, which generally goes deeper. In my undergraduate, we started analysis of functional harmony and worked through analyzing works of Schoenberg & serialized harmony. I *hated* it at the time but even now that I've quit music as a career, I have a tremendous appreciation for it that I doubt I would have if I hadn't been exposed to it in the way I did. I hate a bad frame and didn't appreciate it. I'm actually listening to a Schoenberg mix at the moment on my lunch break... fwiw.
Piano classes consist of some element of reading and being able to play piano music, but it is often subservient to some degree to being able to produce harmony and understand/assist with analysis of the music. It may also encompass utilizing "pop chords" - which denote nothing of how a harmony works in a context but are a prescription for what a particular harmony should be spelled as at a given point in time. This is in contrast with say, roman numeral nomenclature which indicates context almost exclusively without prescribing much of anything for how you want to get there. (e.g. in the former you might see two measures with Cm F7 Bb which might be represented as ii V7 I. The latter provides the harmonic context but doesn't indicate voicings whereas the first only provides context when you have the whole of it provided to you to interpret yourself... I'm not describing this very well but hopefully it gets the picture across).
History and musicology is pretty much what you'd expect. You learn about how music developed over time. It can be very interesting. Ironically, my history class was one of the reasons I quit music. I was doing a masters at the time and I enjoyed it to be perfectly honest, but I didn't see it as being particularly meaningful. That isn't a slam on people who do it because I think its important --- just not my cup of tea so to speak. I actually had a tremendous history professor in my second bachelor's degree who had an undergraudate in musicology & organ performance but then went on to get a PhD in History. I very much liked the direction it took him because he could take what was going on musically to inform what was happening say, sociopolitically. Using it as markers for how to group things almost. Something you wouldn't think to do without a fairly deep knowledge of how to analyze music.
The difference between these disciplines is largely how much of the others you do at the same time. In order to get an undergraduate degree, there really isn't too much of a difference between the degrees often. (Again, the exception sometimes being education because of legal requirements for certification). In the masters level, you can often focus nearly exclusively on that subject. Masters programs are often about "how to be a good scholar" or preparation for PhD. Taking the university as a whole, some masters programs are more-or-less job training. My wife took one in TESOL and it didn't prepare her very much for a PhD if she did want to pursue one (which she doesn't --- she's switched career). Others are less heavy on the applicability and more focus on how to write in a scholarly manner as well as familiarize you with the content of the field.
Once you get to the PhD level, you are expected to know more-or-less a very wide amount of content for your area of focus. You then dig down into a particular element of it. There is little that you learn about say, playing the trombone in a PhD that you wouldn't get from a masters program. It is usually about preparing you for your comps and getting you to think like a scholar as well as immerse you in the field academically. There often is a component about preparing recitals in both the masters and the PhD level which I can't speak to as I don't have a PhD
So I'm not suggesting that the actual performance of music takes a back seat to the academics but from what I've observed, the focus is absolutely on scholarly research at that level.