As Higgins wrote in 1961:

"All of the series is used to provide movements and sounds which can be produced by or with the human body. No external mechanizations are to be employed except for illumination purposes. All markings on the face of the notation are to be considered as notation, and all elements of these markings are to be used or deliberately ignored for the production of movements and sounds according to any consistent system which the individual performer devises for the notation he is using."