Grand traité d’instrumentation et d’orchestration modernes, abbreviated in English as the Treatise on Instrumentation (sometimes Treatise on Orchestration) is a technical study of Western musical instruments written by Hector Berlioz. It was first published in 1844 after being serialised in many parts prior to this date and had a chapter added by Berlioz on conducting in 1855. Many composers studied the work closely, such as Modest Mussorgsky, Gustav Mahler, Richard Strauss, and Nikolai Rimsky-Korsakov.