The Troping Hypothesis
The troping hypothesis produced a distorted picture of medieval polyphony by undue emphasis upon the use of a cantus firmus, or rather, upon the fact that a cantus firmus is used while neglecting the differences in the way it is used. There has been a strong trend since the war to revise the troping hypothesis in certain respects. One of the most important steps towards reconstruction is to become familiar with the manuscript sources—sources that the originators of the troping hypothesis knew intimately. It is important to be clear about the over-all relationship between a set of tropes and its Introit. Introit tropes are rivalled in quantity in the earlier sources by tropes to the Gloria in excelsis. While Gloria tropes are very similar to Introit tropes, they are often called laudes rather than tropi, another indication that the Middle Ages tended to keep apart what we have tried to put together.