> raising A440 by 2 beats per second from my fork will give me A442. > > Am I right? > No. You need to raise it to 442.5 (ten cents) or 25% more of the distance you wish to change it. Two tunings for the increase and two tunings to return it to the original pitch. The "visiting ensemble" must pay for three of the four tunings. I used to charge an extra $100. Now I think I would charge $150. You, the house nor the next performer should bear the cost, inconvenience, time, effort and aggravation. Newton (been there done that too often).
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