Soprano voices in opera seria: a corpus-based inquiry into eighteenth-century vocal types
Eighteenth-century Italian opera seria was dominated by soprano voices. Although masculine roles were typically performed by castrati and feminine roles by women, cross-casting was common, producing four soprano configurations in which performers of either sex could portray characters of either gender. We hypothesize that composers tailored their writing both to the singers premiering their arias and to the characters' gender. Using statistical models built on approximately 1,700 arias, we analyze relationships between vocal typology, characters' gender, and stylistic choices, comparing supervised learning methods and selecting ridge logistic regression as our primary model, whose performance is competitive with that of the best-performing alternative while allowing for interpretation and uncertainty quantification of its coefficients. Results reveal an asymmetry: character gender is consistently encoded in the writing, while the singer's sex is barely recoverable. Masculine-character arias feature large melodic leaps, intervallic variability, and wider ranges; feminine-character arias favor higher maximum pitches, minor intervals, and melodic stability. Female singers sang higher pitches than male sopranos, but this correlates more with character portrayal than with physiology.