Equiton by Rodney Fawcett

Equiton is a notation system designed by Rodney Fawcett published by him in Zurich in 1958. It uses a six-degree staff rather than either a pitch-proportional twelve-degree chromatic staff, or a traditional diatonic staff. It uses its own rhythm notation system rather than using the traditional duration symbols. Mark Gould designed a version of Equiton in 2004.

There's a brief description of Equiton on the Music Notation Project site.

There's more info on Equiton on this page, in an incomplete translation. On that same page are depictions of (1) Walter Steffens's notation in an example by Webern, (2) Schoenberg's notation system applied to his composition Pierrot Lunaire , 3) Klavarskribo in a sonata by Chopin and finally (4) a comparative table of a piece by Boulez in horizontal Klavarskribo, standard notation, and Equiton. The images on that site appear to come from a book by Erhard Karkoschka on new music. The book has been translated from German to English.

Mark Gould previously provided these presentation slides (File:Gould Equiton Slides.pdf) about his version of Equiton on his website.

This master's thesis by Kevin Lewis on graphic music notation depicts Equiton in passing.

Equiton is illustrated on the TwinNote site influences page.