Hello all,
I just tuned a Yamaha U3 with a Piano Lifesaver System installed in an old theatre. When I was done, the midsection was about 5 cents flat. After retuning the midsection and touching up a few unisons, the midsection was about 5 cents sharp. This ended up happening a few times more until I unplugged the dehumidifier. What I think was happening was that the dehumidifier bar was warming the strings in the tenor and then when it was cycling off, the strings were getting cold again. The temperature in the room was about 15 degrees (that's around 59F for you Americans).
This brings up a few questions:
- Does anyone regularly unplug the PLS or at least the dehumidifier bar when tuning an upright? I imagine that even at a slightly warmer temperature, 16 or 17 degrees Celsius, there would still be pitch swings, just not as large.
- Has anyone heard of pitch fluctuations while a piano is being played? Obviously when all of the case parts in an upright piano are attached, it would be easier to maintain a constant temperature inside the instrument. However, presumably as the outside temperature drops, there would eventually be a point in which you would see the pitch change along with the cycling of the dehumidifier.
- I am a little concerned that having tuned the piano in its "cold" state, the midsection will be out of tune once the piano reaches it's stasis temperature with the case parts on. I didn't go back later in the day to check, but I'm wondering if there was some way for me to tune the piano in a more stable way. Maybe try leaving the kneeboard and upper board on while tuning the piano?
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Peter Stevenson RPT
P.S. Piano Service
Prince George BC
(250) 562-5358
ps@pspianos.com------------------------------