It’s an almost unbelievable statistic, but according to Professor Laurie Stras, an academic at Huddersfield University and noted authority on the subject, some 20 per cent of the female population of Catholic Europe in the 15th century lived in convents. If you limited the survey to women of noble birth, the figure rose to a still more astonishing 50 per cent. And what were all these women doing in their convents, beyond study, prayer and sleep? They sang around the clock – creating and performing a vast catalogue of music that, Stras complains, has been ignored by history.