In summer humidiy is high and pianos are sharp; in winter humidity is low and pianos are flat. That's life. My solution: Tune piano as solidly as possible where it is (assuming we're not too far from A-440). I do not believe in pirch changing piano every time I tune it. Not good for piano; not good for tuner. For performance pianos I put them right on A-440 and resist mightily those visiting artists who want me to put our concert instruments at non-standard pitches. So far, the powers that be support me in this.
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