instrumentation

Instrumentation refers to which instruments are called for in a composition — the forces required to perform it. A string quartet requires two violins, viola, and cello. A standard big band requires five saxophones, four trumpets, four trombones, piano, bass, drums, and guitar. The choice of instrumentation fundamentally shapes a work's sound and character. Instrumentation is related to but distinct from orchestration (the art of assigning musical material to instruments). A composer decides the instrumentation first (which instruments to use), then orchestrates (which instruments play which notes). Unusual instrumentations can define a work — Schubert's Trout Quintet uses the unusual combination of piano, violin, viola, cello, and double bass.