The Vienna Opera in 1923 was performed by Richard Wagner’s opera “Lohengrin”. The end of the show was very spectacular: Lohengrin leaves the stage on a white swan. At one of the performances, this party was sung by Leo Slezak, and whether the actor stumbled, or whether the mechanic rushed - the swallow sailed behind the scenes alone. The swallow was immediately found, he turned to the opposite scene and sang with a recitation: "Say, please, when does the next swallow go?"