The prompter in an opera house gives the singers the opening words of each phrase a few seconds early. Prompts are mouthed silently or hurled lyrically in a half-voice, audible (hopefully) only on stage. (This's in contrast to the prompt in a spoken-drama theater who aids actors who've forgotten their words or lines.) Opera prompters are traditionally housed in a stuffy wooden box at the center-front edge of the stage, above the orchestra pit. They're visible to the performers and no one else.… (More on Prompter)