One year we had a young woman who was getting a singing group together for the Ithaca Festival. She picked up singers from many local groups, but, since she didn't want female tenors, she had to make the female tenors into altos. This left her with a fairly small tenor section, so she had some of us baritones switch to tenor. I was one of her ad hoc tenors but I had to switch to falsetto for some of the higher passages. In the process I noticed that my crossover point was higher on the way up than it was on the way down. That is, while I could sing up to (say) a middle C in chest voice before I had to switch to falsetto, if I were in falsetto, I could make it down to maybe an A below middle C before I had to switch back to chest voice. I commented to her that I had hysteresis in my voice. When she said that she didn't understand what I meant (I am used to this which is why I indulge so often in exegesis) someone else commented that I meant that when I was singing my throat heated up.