Dies was a great admirer of the music of Joseph Haydn and during his Vienna years he undertook to meet the composer and write his biography. He obtained an introduction from his fellow artist Anton Grassi, who had made a number of busts of Haydn. Over the course of three years during Haydn's old age (starting 15 April 1805, ending 8 August 1808), Dies made a series of 30 visits to the frail and ailing composer, even though Haydn was convinced no one would be interested in his life story. On a number of occasions Haydn was unable to see him, but frequently Dies was admitted and was able to interview him. In 1810, one year after Haydn's death, Dies published a biography based on what he learned in his visits (see References below). This work is organized around the sequence of visits, reporting each in turn. It continues to serve as a substantial source of information on the composer's life.