I just checked. I haven't played anything all day. I hummed what I thought was E and I was 1/2 step low BUT the acoustic I play all the time is tuned 1/2 step low.
I was a voice major but I didn't completet it. However I used to sight read most anything. I guess all that training made a difference.
I think with just a little practice I could do it, I've never really tried before.
 
J