In this episode, Goodall charts the development of the oldest intact form of music, the 'Gregorian' chant. He reveals how medieval musicians built up the basic elements of music until the explosion of secular folk music outside of the church between 1000 and 1600 AD transformed the world of harmony, rhythm and tone. Goodall reveals how, with the development of ever more sophisticated instruments, it was possible for Monteverdi to write the first successful opera in 1607.