Pier Francesco Tosi was a castrato singer, composer, and writer on music. His Opinoni de' cantori antichi e moderni... was the first full-length treatise on singing and provides a unique glimpse into the technical and social aspects of Baroque vocal music.
Title plate from the English Translation of Tosi's singing treatise, Observations on the Florid Song, first published in England in 1743.
A castrato is a male singer who underwent castration before puberty in order to retain singing voice equivalent to that of a soprano, mezzo-soprano, or contralto. The voice can also occur in one who, due to an endocrinological condition, never reaches sexual maturity.
The great 18th-century castrato Farinelli, painted by Bartolomeo Nazari
A Byzantine castrato from the 11th century
A caricature of Farinelli in a female role, by Pier Leone Ghezzi, 1724
The castrato Carlo Scalzi, by Joseph Flipart, c. 1737