The production "In Rehersal" shows Pierre Boulez working with the Vienna Philharmonic Orchestra on Alban Berg's "Three Orchestra Pieces, Op.6" and his own personal composition "Notations I-IV". Music of the 20th century in the magnificent atmosphere of the Wiener Musikvereinssaal. In an extensive interview, Boulez discusses to what extent he as a conductor bears responsibility for the overall sound and balance of a great orchestra and how he can influence the orchestra's performance. In another interview held in Alban Berg's former apartment in Vienna, the conductor speaks of this master of the "New Vienna School" whose work he values so highly and the origins of his own personal work "Notations", created in 1945. "I like the type of danger you experience when conducting... you have no time, you must do nothing but concentrate", he says of the excitement that accompanies the live performance of a musical work.