Castagna was the daughter of Luigi and Maria Catacchio, and studied piano in Milan prior to turning to singing as a career.
She debuted at the Teatro Communale in Mantua in 1925, singing the role of Marina Mniszech in Boris Godunov by Modest Mussorgsky.
[1] That same year she began appearing at the Teatro Colón in Buenos Aires, singing such roles as Zita in Gianni Schicchi, Bersi in Andrea Chénier, the shepherd in Tosca, Anciana in L'amore dei tre re, and Amelfa in The Golden Cockerel.
There she would go on to perform a variety of roles, both major and minor; she would also take part in the world premiere of Il Dibuk of Lodovico Rocca in 1934.
Among the roles which she took on during this time were Amneris in Aida, Azucena in Il trovatore, Adalgisa in Norma, Laura in La Gioconda, Ulrica in Un ballo in maschera, Leonora in La favorita, Carmen, and Delilah in Samson et Dalila.