Lettrism was a response to what the Lettrists saw as André Breton control of surrealism and an attempt to popularise poetry. The lettrists worked in a variety of forms including sound as well as graphic arts involving letters.
Isou travelled to Paris where the Lettrist movement was formed. A split in the movement lead to the formation of the Lettrist International.
Lettrist works include Lexique Des Lettres Nouvelles.