Piano/Keyboard player in all styles.(questions to bands wanting keys) (San Gabriel Valley & Inland Empire)

Hello.
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I am curious to know what do you expect from a keyboard player when your songs are played.
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Memorize the arrangements? or 2)let the keyboardist to come up with his own ideas?.
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That's fine, but by then those "ideas" have to be remembered on the same song each because --"other ideas'' will come up.
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The best is to play each time the same arrangement of course .
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it is the reason why charts are written .
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to play the same arrangements each time.
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So weather its me or others, we have to listen each arrangement and write it down so it will be played the same way each time.
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PS I am not trying to criticize, only to show the way it suppose to be done correctly.
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Now ,.
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in the other hand, if you let the keyboardist play what he feels each time and changes ideas each time he plays the same song, then ignore the above .
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and everybody will be happy.
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Lol