It was just a short scene in a movie, in which a diminutive actor utters a few unscripted words to the orchestra leader, reciting a line that went down in history: "Wait a minute … you ain't heard nothin' yet." But it was a scene that changed the entertainment world and heralded the dramatic arrival of sound to the movies.

Never again would audiences have to read "titles" to explain the action or translate the sweet nothings of lovers. In the space of just over an hour, the silent film was dead.

The moment occurred 90 years ago this weekend. The owners of rival studios had thought their competitors at the near-broke Warner Bros were going out of their minds. The idea of Warners featuring Al Jolson, the biggest star on the American musical stage, actually singing in an upcoming film was madness.