Whether imposed externally, by virtue of monopoly franchises or censorship laws, or whether imposed voluntarily by actors, directors, or producers, these restraints have taxed the creative minds of the theatre to tackle the challenges of working with and around them.
In the Elizabethan theatre of Shakespeare, a similar ban forbade all actresses from appearing on stage, at all; the parts of women were generally played by boys.
In the markets and fairgrounds, itinerant actors created a new theatrical form by holding up cue-cards (like sub-titles or karaoke) containing the words of the plays or songs, which the audience then acted or sang for them.
This became even more successful, with crowds coming from all around to see how the actors had overcome such rigid censorship.
Some of the restrictions, or traditions born of them, may have still been in place in the nineteenth century, at least if Marcel Carné's Les Enfants du Paradis is a reliable guide.