What's your vocal range?
i have never done a formal test but i know it goes really low and just a little bit up. the next song explores a little bit of this but doesn't push any limits.
on a related note, i've noticed i usually sing in the octave above what i probably should be singing in, but oh well.
this also reminds me of that one song idea that goes really low then takes a very quick transition to a very high part that i don't think i can sing.
ask me again in a few weeks and maybe i'll have a range demo prepared.