Possible Clues:

• Part of an orchestra conductor's job description?
• Prudent advice to a first-time music conductor?
• A conductor has to be aware of the essential facts...
• A Wimbledon umpire should be well-informed
• Rehearsed orchestral players will appreciate the situation
• A tennis umpire should be well-informed?
• Be informed, as should an orchestral musician?
• The orchestra was in turmoil; the conductor didn't ___..
• Be well-informed
• Understand -- as should a conductor?