Just a note: I was forced to convert to Sierra over the last several days (Microsoft Office crashed—>Microsoft demanded I go to Office 2016—>required Sierra). If you’re in this situation or contemplating changing, understand that under all that happy talk about neat, neat new functions, Apple sets your system back to its basic settings. I lost my A to D interface driver. Being new to audacity, I wasted two hours of studio time (yeah, I know, what was I doing in a studio using Audacity?) before I realized that I’d reverted to Apple’s far inferior A to D converter. So, word to the wise, be vary, very careful when converting.
I managed to avoid “ugrading” so far. The system upgrade appeared in some surprising places. You do need to pay attention.