Beechnut,

One thing that needs to be remembered is that not only country determines country. Other markets change. The "Pop" catagory changed to harder edged acts around the Anne Murray time. In my own experience, the country catagories changed enormously when other catagories changed. When Seattle grunge music took over the rock and pop airwaves, many groups like Alabama, who might have been considered rock ten years earlier, were pushed to the country airwaves.
All music adapts and changes. It is never just one format that determines those changes. It is an entire business model and the general public. And since all these elements generally compete with each other, it is rarely one person or entity that makes the determination. You find generally it is incremental and happens over a longer time period.

MAB