The audio signal goes in with positive wire and backs out with negative wire.
That is not correct. During one half-cycle of each of the frequencies that is present the current corresponding to that frequency flows in via the positive conductor and out via the negative conductor. During the next half cycle of each of the frequencies that is present the current corresponding to that frequency flows in via the negative conductor and out via the positive conductor. The directions of the current in each conductor continue to alternate during successive half-cycles. Meanwhile, energy is transferred in just one direction, from source to load (assuming the load is resistive), with the alternating flow of current through both conductors being essential to that process.
BTW, the "positive conductor" is often referred to as the "signal conductor," and the "negative conductor" is often referred to as the "return conductor" or "ground conductor," but the electrons and the energy that is being transferred don’t care about names.
Regards,
-- Al