The tradition of analogue projection is a bit scattered and uncollected. In essence there are two main historical precedents or influences for 4shrooms: 1960s light shows and La Trinchera from Mexico City.
The concept of freely layering multiple media of analogue visuals derived as a thought experiment from Doris over the years. This finally came into being with a series of performances that resulted in the formation of La Trinchera, a group based in Mexico City. With co-founders Rafael Balboa and Manuel Trujillo, they created a table of different means: slides, 16mm and OHP, and performed with accompanying experimental sound. The group has since expanded to include Aisel, Elena, Viviana, Azucena.
In late 2006, La Trinchera visited Vienna to perform at Sammlung Essl. The video (20Mb) remains one of the best documentations! Out of that experience, Doris and the invited artists from Vienna (Anna, Georg, Jan) formed 4shrooms.
Georg is a long time 16mm projection artist, and has the distinction of being the granddaddy of projection for 4shrooms. His 16mm tradition stretches back 20 or so years.
Georg is currently working on a History of Projection. Forthcoming!
A rather similar development happened in the late 1960s. With the sixties, the psychadelic experience led to the evolution of light shows. The most famous of these was the Joshua Light Show, led by Joshua White. The group worked primarily as an accompaniament to the bands playing at the Fillmore East in New York. Their favourite technology was oil-and-water mixes.