First of all, you can take one course from group 1 only if you are also taking a course from group 2 (foreign language acquisition), either as Language AB initio or Language B. Either way, you have to take two language courses. You can do that with two Language A courses or with one A and one B course.
You can ask for an exception from the IBO, but I highly doubt that you could get a positive responce from them. Normally you won’t be eligible for the IB diplome. Your future school’s or the current one’s IB Coordinator could do those kind of inquiries.
I’m guessing that you’re taking Chinese/Cantonese SL as a language A course. If that’s not the case, if you’re taking it as a foreign language course (therefore as a language B course), you might consider to take the corresponding IB exam in May 2018. Some schools have this option: if you are a good student in a foreign language course, you have the option to do the accelerated version of the course. You take the same course with other juniors, but at the same time you do on your own all the other stuff that the seniors do (IAs, exam preps, etc). Of course, you take some counseling on what to do related with the stuff you’re doing on your own. Check your options with your current school.
If Chinese is not your mother tongue, another option might be dropping it asap from Language A to Language B course and take the IB exam at the end of the school year. In fact even if it is your mother tongue but you are not really bilingual (therefore if your English is better than your Chinese), you could still do that. It all depends what your current school administration will say.
Otherwise, you can search for an online IB Chinese course that you could participate next year. One such company is Pamoja Education, but they don’t offer Chinese if I am not wrong. Maybe, if you have some knowledge on French or Spanish, you can take French or Spanish AB initio with them (if they accept you as a student after two months of the start of the classes). In that case, you should drop your Chinese course of course.
One last option is to find a private teacher for the next year who could do IB Chinese private lessons with you each week. In our school there are some newcomers who cannot continue with our school’s foreign language options since they have not studied them before. So, they take 5 courses from the school and study their own mother tongue’s IB Language A course with a private teacher. But bear in mind that this private teacher should be recognized as a proper IB instructor by your new school. So it is not a thing that could be arranged at the last minute. You should plan and arrange all this stuff
I’m not sure if an IB music course of one year is a feasible option. If you find an alternative for your Chinese, you can forget about the music course. But if all my suggestions about the second language course do not work out for you, you can check out if you can replace an IB course with an AP course. Again I doubt that it is allowed as a 6th course (doable as a 7th course though). But if it is, you can take AP Music class. There are online versions for this one too.
I think you should inquire these options asap. Also you should decide on your next year’s school asap. You may be late if you didn’t do anything yet for applying to the high schools.
I’m sure you’re aware that changing school (and your residence) in your senior year is not a small thing. You’d better to discuss it further with your parents. If there is nothing else than the limited subject choice in your current school, I would reconsider the whole thing. Don’t forget that finding the same IB courses in another school will not be an easy job. You may see that lots of school will also have limited choices of courses. For example, our school is a very big IB school but we don’t have IB Business Management course (or IB Chinese). Most schools you will find will lack some courses from your list (or they will have physics for example but only as a SL course). And the courses will not be only problem. Emotionally, being the new kid at your senior year will not be easy. You will probably get some difficulties in getting good EC positions as well.
Any way, good luck.
(sorry for the long passage)