The gradual average is produced by gradually overlaying all the cassettes. Every minute a new cassette file is overlayed until we obtain a superposition of twenty cassettes. Then the layers are progressively removed and new ones added until all cassettes files have been added and removed.
The following image shows the order in which the different cassettes are overlayed (horizontal: the minutes of the stream, vertical: the cassettes)
Sample
A series of scripts and agorithms have been written to create different radio programs based on the audio material collected and created by Erkki Kurenniemi