Alternating current is really DC that reverses polarity 60 times a second in this case:
30 times a second, hot is +, neutral/ground is -.
30 tmes a second, hot is -, neutral/ground is +.
However, what kills you is the current across your body, not the voltage polarity. You're body reacts the same whether your feet are positive and your hands negative, or the reverse.
This is why people often survive lightning strikes to their bald head (millions of volts), yet die while welding (20V, 120A).
Anyway...
You're confusing the concept of "Ground". In DC circuits, "ground" generally just means "shared negative voltage buss", which is often the chassis of the radio, or whatever. In Jaguars, for example, "ground" is "positive battery potential". Yet, its still ground.
In power AC circuits, ground is earth - the planet all your stuff sticks to via gravity.
That's why in DC circuits there are two ground symbols, one for earth, one for chassis.
Maybe this will help... alternating current flips between scenario 1 and 2, as the current's polarity alternates many times a second.
Scenario 1:
HOT (+) -----------> your left hand
NEUTRAL (-) -------> your right hand
Ground (-) ---------> your feet
Scenario 2:
HOT (-) -----------> your left hand
NEUTRAL (+) -------> your right hand
Ground (+) ---------> your feet
In both scenarios, regardless of polarity, the voltage potential (delta) between your right hand and your feet should be zero. And you can measure this with a voltmeter right at the breaker box.
The voltage potential (delta) between hot and neutral is 120V, and between hot and ground is 120V, so touching hot and either (or both) of the other two lines can kill you.
Note that the voltage doesn't kill you, its the current that goes through your body that does. If you're healthy, your body can survive a million volts at 1/10th milliamp no problem. And 1 volt at 100A will turn you into an "extra crispy" speciman.
If you were to measure this at your breaker box, you should see 120V AC between Hot and Neutral, and Hot and Ground. And 0V between neutral and ground.
Polarity is irrelevent, its voltage delta. Your body doesn't like electricity going through it whether your hands are positive and your feet negative, or the reverse.
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Now a side comment relating to recording. If you attach your volt meter between neutral and ground at the breaker box, you should see zero volts AC.
However, further down the wires (at the outlets in your studio), you might actually see some voltage. THIS is what causes hum in audio gear.
HOT ------------ small wire resistance -------------- \
Neutral --------- small wire resistance -------------- - outlet
Ground --------- small wire resistance -------------- /
Different lengths of wire, introduces different amounts of resistance, which in turn, creates different neutral-ground potentials, an in turn, adds to the hum problem.
In fact, every wire nut you add between your outlets and your breaker box, adds to the resistance a very tiny amount - and in turn, allows for more hum.
DON"T GO THERE STEVE!! 
It won't do anygood. Old farts on batterys can't change thier "polarity". Ha! 
