Fischer-Dieskau also performed many works by living composers including Benjamin Britten , Samuel Barber , Hans Werner Henze , Karl Amadeus Hartmann , Ernst Krenek and Witold LutosÅ awski . Fischer-Dieskau also performed many works of contemporary music , including Benjamin Britten , Samuel Barber , Hans Werner Henze , Karl Amadeus Hartmann ( who wrote his Gesangsszene for him ) , Ernst Krenek , Witold LutosÅ awski , Siegfried Matthus , Winfried Zillig , Gottfried von Einem and Aribert Reimann .