Ubuntu Studio is a version of Ubuntu especially for audio production. https://help.ubuntu.com/community/UbuntuStudio
I've experimented with Linux at length, because I too like the philosophy of openness. Unfortunately, the result of this openness is that it's extremely hard to get anything done, and most of the really useful software is not available. I've given up trying to make it work for me. It's fun to experiment with. It has some of the benefits of Unix, with a few similarities to other GUI-based systems like Windows and Mac, but in my opinion it's not really a suitable operating system for anybody except programmers and people who work primarily in the command line.
You're right that Windows is still the biggest platform, but the situation is changing. Not only is Windows losing market share to Mac OS and Linux, but more significantly, many people who used to use a standard Windows PC now use a tablet or even a smart phone instead. I know many people who now use their table for most "computing" tasks, and only use their desktop computer rarely, for things like printing out big documents, or filing tax returns. For other things, they use portable touch-interface devices. The world of personal computing is changing.
You don't have to like Apple or use their products -- as we said we each get to use what we like -- but to dismiss their influence in the world of computing is silly. They are not only the largest computing company in the world, not only the biggest technology company in the world, but the biggest company of any kind, and still growing.