The duration of an orchestra rehearsal can vary based on several factors, including the complexity and length of the musical pieces being rehearsed, the size and experience level of the orchestra, the conductor's preferences and rehearsal style, and the goals of the rehearsal. Smaller community or amateur orchestras might have shorter rehearsals of 1-2 hours, while professional symphony orchestras can have longer rehearsals of 3-4 hours or even more for particularly complex or high-stakes performances.