The terms “arranger” and “orchestrator” are frequently confused.
Orchestrator Larry Blank explains the difference using the song “Singin’ in the Rain” from the eponymous film. The composer and lyricist are charged with writing the actual song (“I’m singin’ in the rain, just singin’ in the rain…”). The arranger creates the intro before the song begins. And the orchestrator decides that flutes should play that intro before the song begins.
Responsibilities of a Musical Arranger
In general, arrangers work primarily on enhancing songs and scenes with additional musical material. For example, if a song requires an ensemble to sing harmonies, an arranger will write the harmonies for said ensemble. If a number requires a dance break, an arranger will work with the choreographer to create the music for said dance break. If the director wants underscoring for a scene, an arranger will work with the director to create the music for said scene, while seamlessly blending into the existing song’s style.
Responsibilities of a Musical Orchestrator
In general, orchestrators work from piano/vocal scores prepared by the arranger and composer. Orchestrators will work with the composer and producers to determine instrumentation for the show as well as the number of players available. While they may receive some notes/ideas from the composer and arranger, the orchestrator are the primary decision maker all existing musical instrumentations, from songs to scene underscores.
The arranger works frequently with members of the creative team such as the composer/lyricist, choreographer, and director rather than the orchestra. In contrast, the orchestrator primarily works with the orchestra, composer, and arranger rather than the director and choreographer.