Self-taught mostly!
I started out making beats with a really old program called midimaker, it used stock midi sounds (lol) but I could at least get melodies out of my head that way. Then I discovered Reason by accident (version 2.5 back then), and that was a real eye-opener. I started getting more into music production, also learned Logic, all on my own and by reading the manual (it often gets into details that you don't think about checking when you're just playing with software.
Then during my University time (I was studying maths) I was in a building with a lot of students from different backgrounds, and some of them were in the conservatory. Since I was into computers a lot, and it was just the beginning of "home recording", a lot of them came to me to help them set-up, record, edit their tracks. I loved it so much that I decided to switch studies and went on to study Audio Engineering. I learned a lot more about music production, audio, how to use a studio, and how to work with people that way. I ended up doing an internship at Galaxy Studios, a major studio in Belgium. I stayed there for 3 years, had the studio for myself in the weekends, recording my friends etc... That was a second eye-opener as I really learned to take my listening to a next-level, and about working in a professional environment.
So, mostly on my own, and by experience of course!
I now make websites for a living, because the pay and work days as an audio engineer were much too harsh, which allows me to do some music in my free time (I started out because I wanted to make my own tracks, so that's really where my interest lies, more than working in a studio). I still plan to make a living out of music one of the days, but hey - we'll see!
Peace,
Speekless