The prompter (French/German: souffleur; Italian: rammentatore, suggeritore) in an opera house gives the singers the opening words of each phrase a few seconds early.
Opera prompters are traditionally housed in a stuffy wooden box at the center-front edge of the stage, above the orchestra pit.
The famed diva swooped down in a curtsy right in front of the prompter's box and – mid-curtsy, unnoticed by the audience – gave the Italian command "più forte!"
[full citation needed] Prompters attend all rehearsals, mark up any adjustments or clarifications to the score, and generally "prepare" singers for a role.
However, occasionally singers or conductors (e.g. at the Met) will acknowledge or bend down to shake their hands during curtain calls of premieres or chorally complex operas.