Know Everyone's Parts
Music Directors need to know all the important parts of a song for all the instruments. They need to know what the Keys player is supposed to play in the bridge, what the drums are supposed to do for each section of each song, and any other key instrumentation for each arrangement. This means music directors have to really study up on the songs...not just learning their own parts, but knowing everyone else's. If you are music directing, please spend the time to really know the songs, the feel of the song, the song structure, the dynamics, and the key parts of the instrumentation.
Error On Over-Communicating
If you're going to error, you want to error on the side of saying more, not less. It's better to say "Ending 2, 3, 4. Big Crash!" then just letting the band end. It's better to say "Bridge 2, 3, 4" then hope that they all remember. Other phrases: "Bass and cymbals", "cymbal swells", "Start the next song", "kill the click", etc. You are the director, so use the mic and give clear direction.
Speak Early Enough
Make sure you are speaking early enough for the band to hear what you are saying, find the correct place on the chord chart and get their bearings. Don't be last minute. Communicate early...and be loud and clear.
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