The real trick is to start flat with a good CD (The Nightfly is still one of the tried and true test CD’s) and don’t adjust it unless someone complains!
One thing to avoid is trying to add any upper and lower end in rooms that have a lot of tile and/or glass. As older players playing for generally older audiences, nothing will annoy and make people struggle to have a conversation over your music more than a lot of high end pinging around the room.
If you’re struggling yourself, unless you got a big budget, a simple set of little in ear monitors can restore some clarity without breaking the bank. $30 or so will do the trick. We don’t move around much as keyboard players, so pretty easy to hardwire them to your PA’s or keyboard’s headphone out (if your keyboard has the mic in and effects).
It’s always better to have the crowd struggle to hear you than struggle to hear each other!
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An arranger is just a tool. What matters is what you build with it..!