Par BOULANGER NADIA. Nadia Boulanger's Three Pieces for Viola and Piano Posterity has retained of Nadia Boulanger only her gifts as a virtuoso of the piano and organ, her skill as a conductor (of vocal ensemble and orchestra) and most of all, her incredible charisma as a teacher. For nearly sixty years, 'Mademoiselle' made the most of her famous Wednesdays, bringing rigour and passion to the tra…