Labels, as Magritte’s famous The Treachery of Images reminds us, are important in art. They help anchor and frame our perception; they generate energy, sometimes friction. In the case of music they help us to hear differently. A Bach Passion in a church is, arguably, an entirely different work to one performed on stage. Ceci n’est pas de l’opera.

Two of London’s most exciting young opera companies invited us to consider this question last week.