Well the tone does physically change because of the proximity effect. Getting closer to the mic boosts the low end frequencies. The spec sheets that come with most mics show this effect.
Some higher notes require more energy, even though they are not above the vocal range. Actually there are many times when lower notes require a little more volume for the situation, so backing off the mic helps there also.
The Crown mic does have some built-in compression. I tried it, but it wasn't comfortable for me.
DonM