The AC signal is carried on the inner pin of the RCA jack
and the ground provides the return path for the complete
circuit. Just as the body of your car carries the return path
for the battery power that runs the starter motor, the power
that runs your lights, and even the audio that goes to the
rear speakers, etc.

The inner pin is just one conductor, correct? Where's the other conductor at?
Is it ground? If that's so, that's what I'm not getting. If ground means
there's a rod stuck in the earth, how can that be generating the other "half"
of the AC signal?

Typical consumer equipment uses UN-balanced connections.
Think of a kid on a pogo stick. The movement is all referenced
against ground. But the ground has to be there even if it
doesn't move. You can't use a pogo-stick in outer space.

I take that to mean that there would be three conductors.
a) Our theoretical ground
b) The conductor which flows electrons left-right when the kid goes up.
c) The conductor which flows electrons left-right when the kid goes down.

But an audio signal is only 2. That would mean that either b) or c) is somehow
combined with a). How would the other device know how to separate the real
signal (b or c) from ground (a)?



My main thing is I don't see how a rod stuck in the ground can generate
the other "half" of the audio signal.