Medieval music has been made and remade over the past two hundred years. For the nineteenth century it was vocal, without instrumental accompaniment, but with barbarous harmony that no one could have wished to hear. For most of the twentieth century it was instrumentally accompanied, increasingly colourful and increasingly enjoyed. At the height of its popularity it sustained an industry of players and instrument makers, all engaged in recreating an apparently medieval performance practice. During the 1980s it became vocal once more, exchanging colour and contrast for cleanliness and beauty. But what happens to produce such radical changes of perspective? And what can we learn from them about the way we interact with the past? How much is really known about the way medieval music sounded? Or have modern beliefs been formed and sustained less by evidence than the personalities of scholars and performers, their ideologies and their musical tastes?