Basically, instead of a pulsed-DC +5v and 0v (5 volt range) signal, driving two pins out of phase yields an effective +5v and -5v (10 volt range).
In concept, you're trying to fake a DIFFERENTIAL LINE.
But I still don't get how you'll generate a -5 volts (with respect to ground), to achieve a +5V - (-5V) = 10V range
EDIT:
you would tie the piezoelectric buzzer to pins 9 and 10 a
Ahhhh okay, sounds plausible (pardon the pun). Demo please. Youtube 