How did people decide which instruments to play with each piece?

People typically decided which instruments to play with each piece based on the composition's style, historical context, and intended emotional expression. Composers often specified instrumentation in their scores, while musicians would consider the piece's genre and the ensemble's strengths. Additionally, performance traditions and audience expectations played a crucial role in determining the appropriate instruments for a given work. Ultimately, the choice of instruments aimed to enhance the overall sound and effect of the music.