"Do we draw the line at music played through technology or are we talking about anything any human being is doing that is within the realm of our hearing?"
The issues are consideration of other people, and what we expect from a wilderness. Some of it is contextual; I know I have to put up with generators, televisions, boom-boxes and singalongs in larger campgrounds. Next on the scale are easily reached trailheads where there might be loud groups fueled by a lot of alcohol. But out in the wilderness, I think I have a right to silence.
The portable speakers present a new and difficult challenge. If a musical instrument or singing is present, it is usually very time-limited and not so loud. But I don't think the "not so loud" standard is as valid when applied to personal speakers. In the wilderness, I don't want to hear "Hotel California", at any volume. The speakers could serve as a too-easy enabling device for people who are the least sensitive to the nuances of context, or other people.
I was recently with a Sierra Club group where the campfire festivities evolved into a quasi-dance affair driven by some small speakers. It was a social activity, and we were reasonably certain that no other parties were present in the empty campground. But I can easily imagine situations where we could have been mistaken about the presence of others. It may be better to just leave the speakers at home.