Don, <<I have data on one Steinway B that has a DC system on it. It was left unplugged during March for "a couple of days". I needed to tune it for a concert--and had gone by to make sure things were working well. It was a "pre bottom cover" installation. The pitch rose 14 cents at A4 in 12 hours. Unfortunately I did not think to measure the first plain steel wire.>> Are you saying that it rose 14 cents after you went by to check it and plugged it back in? Wow! Give me some more details if you can. Could there be some other factor(s) than just a DC system being unplugged for a "couple of days"? Is the piano structurally sound? Do you know what the humidity was then in March? RH in the average dwelling here is anywhere from 25-40% in March. <<I do not consider over one cent of drift per hour a slow change especially not when it may often be double (or more) than that at the first plain steel wire.>> Nor do I. But I've not observed this personally. On the D that I mentioned earlier, it is routinely unplugged out on the stage for performances, then plugged back in after it's over. There have not been any drastic changes like you noted. No one has commented about anything like this happening. I'll be tuning it tomorrow and Saturday, and will observe what happens. It will be unplugged Friday morning, and perhaps through Saturday. However, now the RH is around 42%, so I wouldn't expect any changes like you mention. John Formsma
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