It's definitely a two edged sword... set the instrument up so it sounds good to YOU, directly on top of the monitors, and those out in the room will suffer. Set it up for THEM, and you suffer!

There's no real way around this problem There's no way to add more reverb to the arranger at the mixer's monitor send on most boards, and even this will only muddy things up a hair, as the bass end gets reverb'd along with everything else.

But the bottom line is, are you playing to THEM, or to yourself? As a pro player, your goal should be to do whatever is best for them, and if that makes you less than comfortable, well, that's the price you pay!

You have probably heard me rail many times against user demos (and some factory stuff too, if the truth be told) that have the played part too loud, as players choose to listen to the part THEY are playing at more than it truly needs, and end up swamping the backing. To get a fully balanced mix out to your audience, there really is no way around getting used to things not being what WE want, but being what THEY want if you truly want to have your audience hear you at your very best.
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An arranger is just a tool. What matters is what you build with it..!