Watch VoirFilms. Anton Webern's "Langsamer Satz" for string quartet was performed as part of the "My GAIA" concert during the Festival's 2012 edition. Composed in 1905, "Langsamer Satz" is in traditional sonata form and in the key of C Major; it would be another twenty years before Webern turned to twelve-tone technique. "Langsamer Satz" premiered in 1962, seventeen years after Webern's death, and has the longest playing time of any piece in his body of work.