Preconcert activity typically involves tuning instruments, which is a six-letter word in this crossword. Tuning is the process of adjusting the pitch of an instrument to match the desired sound. This is done by tightening or loosening the strings on stringed instruments, adjusting the reeds on wind instruments, and adjusting the valves on brass instruments. Tuning is an important part of any performance, as it ensures that all instruments are in tune with each other.