voices including adult and youth male and female. Also several demons, giant spiders, pirate spiders, etc. along with multiple regional accents and languages. In one book I even sang a country music duet performed by two teenage girls.
It is partly talent, and partly very hard work to differentiate them in the editing phase. You have to re-record multiple sentences and paragraphs. That is why many voice actors just won't do it. Also, somebody pays for all that time, and they might opt for speed of delivery over quality.
I hope that helped.