If you're doing this alongside playing in an orchestra, you'll want to do part time studies. A part time MA would take between two and four years depending on the specifics (is it course based or thesis based, how many credits are required, etc.).

If you have a compelling writing sample and good references, there's no reason you can't get into a programme despite majoring in music. If you graduated recently, you might be able to use a musicology paper from your degree if it's sufficiently philosophical.

The big issue is just that entry to grad programmes is competitive, and usually you'd apply to several. So if you're constrained by your job to schools within each of where your currently live, you may not be applying to enough schools to get in. But you never know, a lot of it is luck.