I was on the exact same road as you are on right now. I was considering a career in the music field or the engineering field. After putting a lot of thought into the decision, and asking for peoples' thoughts and opinion regarding the two majors/fields, I decided to go for engineering. I will not list the reasons why I favored engineering instead of music, because I do not want to possibly persuade you from doing what you truly want to do (If you want me to give you my reasons, then I will).
I don't really know my scales at all. I'm a drummer for my schools marching band, so scales are not something I have experience with... 
In regards to careers, I agree with the handful of people that have been saying that you should do what you want to do. A good career, in my opinion, is not only about making a decent profit, but it is also about having fun with what you want to do. As of now, I plan on going to college for mechanical engineering (maybe a double major in education), so I can be a physics teacher and/or an engineer when I become older. As it has been said before, do what you think is best for you, and do what makes you happy.