Just so you know, my kitty Jake (9 years old) came down with a herpes outbreak and ever since then, his voice has been raspy. It doesn't look like it's going to ever come back. It's a shame, because I loved his voice and he's a vocal boy too, but he's had a full workup, and he's healthy otherwise. :sad:
I agree with the others though, Paco might be sick (like Jake was when it happened), and a full workup is a good idea.
Good luck - keep us posted!