For the composition Mantra, a work commissioned by Karlheinz Stockhausen for Südwestfunk (1969), Haller built a sound transducer with the engineer Peter Lawo.
Halffter's Planto por las Victimas de la Violencia, the first work with electronic spatial sound control, was premiered at the Donaueschinger Musiktage.
[3] From the early 1980s onwards, the Experimental Studio produced Luigi Nono's entire late work, who compared Haller's importance for these compositions to that of Joseph Joachim for Brahms' Violin Concerto.
In addition to Nono, Haller also worked with composers such as Pierre Boulez (Répons), Kazimierz Serocki (Pianophonie), Brian Ferneyhough, (Time and Motion Study), Dieter Schnebel (Monotonies) and Emmanuel Nunes (Wandlungen) together.
At the end of 1989, Haller took early retirement to write a documentary about the Experimental Studio and the research into electronic sound transformation on behalf of the Heinrich Strobel Foundation.