Soprano is anything above contralto. Mezzo is short for mezzo soprano, a subspecies. Most soprano singers can also sing down to the G below the staff, but should do so only very carefully, to avoid "isolating their chest register". --

Morwen, you wrote on another thread that you have access to the Sibelius software, so you can do the transposing and slowing-down yourself. --

I have just opened a new thread about "Little Software Helpers?", which may attract many of our computer freaks.