They collaborated on more than 50 theater productions, including Pinkville (New York 1970, Berlin 1971), Sigmunds Freude (Bremen 1975), The Sinking of the Titanic, My Mother's Courage, Improvisations on Shylock (Munich 1980-81), Jubiläum (in which Walden acted a major role) and Peepshow (Bochum 1983-84).
Walden then went to the Vienna Burgtheater with Tabori and Claus Peyman, where Mein Kampf, Ballade der Wienerschnitzel, Requiem for a Spy, and The Goldberg Variations (1991) were produced.
In Tabori's own theater, Der Kreis (The Circle), they collaborated on Masada, Lear's Shadow and For the Second Time, in which Walden starred with Hanna Schygulla.
Walden also composed the chamber symphony, After Auschwitz, which was performed at the Eastman School of Music at the University of Rochester (New York).
It was also performed by the Budapest Strings Chamber Orchestra in Cividale del Friuli, Italy and by the Brandenburg Philharmonic in Potsdam, Germany.
(1989), Miami Lights (with Jacques Levy, 1990), Café Mitte (with Volker Ludwig, 1997), Claire (with Manfred Karge (Bochum, 1985, also Ghent and NDR TV), Die Bettler Oper (Renaissance Theater, Berlin, 1985), The Goldberg Variations Musical (Tabori in Karlsruh, 2016) and Butterfly Madam (with B. Peachy, Palm Springs, 2011) Walden's film scores include David Newman's La fille d’Amérique (1977), Vadim Glowna's Desperado City (1981), which won the Caméra d’Or in Cannes and in which Walden also acted, and George Tabori’s Frohes Fest for German public service television broadcaster ZDF.
In 1998, collaborating with Barbara Walden, he published the book Life Upon The Wicked Stage, which has become a standard work for training musical actors.
The parents of two sons, Matthew and Joshua, the Waldens lived in New York and Berlin before moving to Palm Springs, California, in 2007.
Tributes took place in the United States and Germany: Barge Music in New York City (September),[8] Baltimore Lieder Weekend (October) and Leipzig (November).