Here is a good graphic illustrating the difference between variable density and variable area recording. The source of the image is Wikimedia Commons.
Update I realize the title might be a bit confusing. The image on the left is variable density, that on the right, variable area.
Thursday, June 25, 2009
Excerpts from Erno Rapee's Encyclopedia of Music for Pictures (1925).
Rapee was one of the most influential music directors in the New York picture palaces in the 1920s. He published two practical books on the subject, one meant for pianists and organists (Motion Picture Moods (1924)) and one for theater music directors (orchestra leaders), the Encyclopedia. I have posted the text of his long introduction to the Encyclopedia, a complete list of the topic categories (types of music, such as "mysterious" or "Oriental"), scanned graphics of pages for the entry "Agitato," and a text file with the works listed under "Love Themes."