The last 15 years of his life he worked as a composer only. In 1973, his first tape was published. In 1974, he composed the music for the film Der Untergang des Alpenlandes. In 1975, Bert Breit invited him to compose the film music about Tyrol, for which he composed the "Streichquartett für Bläserquintett", PWV 15.
In Austria Pirchner was well-known, since he composed the "Sounddesign" for the ORF-culture radio Ö1 in 1994. In 1995, he composed the music for Hofmannsthals Jedermann at the Salzburger Festspiele.