Pierre Boulez was one the greatest conductors, composers, and music theorists of the 20th and 21st centuries. He revolutionized performance approaches to the music of composers like Mahler, Debussy, Bartók, Ravel, and Stravinsky, and was instrumental in transforming the Parisian musical landscape through his advocacy for monumental projects like the Opéra Bastille, the Institut de Recherche et Coordination Acoustique/Musique (IRCAM), and the Philharmonie de Paris. He died on 5 January 2016 in Baden-Baden at the age of 90.

The "In Rehearsal" series captures some of today’s leading conductors in rehearsal, artists like Valery Gergiev, Esa-Pekka Salonen, Roger Norrington, Pierre Boulez, and Christoph von Dohnányi. Giving viewers a unique insight into the process by which conductors create an interpretation of a given work, these films document the different conductors’ unique styles and ways of working with an ensemble. Most episodes include a full run-through of the work rehearsed as well as interviews with the maestros themselves!