That's correct. Even played back to back, you'd have a very difficult time telling song played on instrument tuned to 440 Hz from the same one tuned to 432 Hz.
Yeah, that stuff about resonant frequencies (of DNA?) is complete bunk. DNA is so tiny it's resonant frequency would be in at 100s of MHz (the resonant frequency of water is around 2.4 GHz). Plus each thing, say a person's ear drum (since we're talking about hearing) is unique. The unique properties changes the resonant frequency. So even if one person did tune A to a factor of the frequency at which their ear vibrates with the least energy required, it's not going to be the same for the next person. Oh, and you don't want to listen to a sound that resonates your tympanic membrane for very long--it's not a pleasant feeling.
I imagine if one were to resonate their DNA, it would denature it (just like putting too much energy into any protein, it unfolds, and it's it the very folded shape that makes the protein work), and cause cancer.
