Make it up as you go along...

Classical music has a problem with perfection. You'd have thought the most important job of any professional musician was learning, playing and repeating the notes composers wrote down so often that they become second nature. Surely that's how the tradition works: keep playing the same music – by Strozzi, Bach or Vivaldi – over and over again until the jewels that they left us are polished to a gleaming finish. That's what the works of classical music are all about: they are bound in the pages of scores, fixed as absolute sequences of pitches in time, and turned into objects of contemplation in performance by classical music's ideals of recreative execution.

- Tom Service

Well... for nearly all the music written down before c.1820, that's a model of musical culture that's anachronistic, ossifying and just plain wrong. The notes that composers from Monteverdi to Mozart left us aren't absolute, but conditional. Many of their scores are deliberately incomplete, designed to be finished in the moment of performance by the musicians themselves. Those aren't extra or optional requirements; they are demanded as part of the process of making music. Instead of relying upon players and singers merely to realise what's on the page, these repertoires are about asking them to be part of the creative work itself. If you