Picture and Sound Rushes (1971) includes synchronous sound footage of Fisher explaining the premise of the film that is being shot. He improvises his dialogue from notes to which he refers while the camera is rolling. At predetermined thirty-second intervals, the film alternates between sync sound, wild sound over black, MOS or silent footage of Fisher speaking, and silence over black. After the segments of silence over black (called the “null case” in the film) Fisher’s reappearance comes as something of a relief.
[Source: William E. Jones, "Morgan Fisher: An Impersonal Autobiography"]