The main character in Orfeo (Orpheus) was a castrato. Look up what a "castrato" is online and then answer this question - it may shock you!

A woman posing as a man to sing high notes
A person with a high voice singing offstage while the performer on stage lip sincs
A man who sings in a falsetto voice
A man who voluntarily was castrated before puberty to keep his voice high

A castrato is a man who voluntarily underwent castration before puberty in order to keep his voice high-pitched and retain the vocal range of a child. This practice was common in the Baroque era and was done in order to create singers with an exceptional vocal range and power.