 He made as many as fourteen separate sound tracks.On one he had recorded fifty women shrieking; on another the groans of as many men; a third consisted of a dozen violinists scraping their bows across the strings on a single screeching note.These various tracks had then to be blended in different volumes and intensity until they produced a noise which seemed to him to resemble - on what authority is uncertain - 'the lid of hell being opened'.