orchestration refers to

The use of dynamics
A soloist
A choir
What instruments are used

Orchestration refers to the arrangement and selection of instruments in a musical composition. It involves determining which instruments will play specific musical parts, as well as how they will interact with each other and contribute to the overall sound and texture of the piece. Orchestration also considers factors such as the specific range, color, and timbre of each instrument, as well as the desired dynamics (volume and intensity) and the balance between different sections of the orchestra.