Sometimes artefacts of the piano tuning process can cause perceived frequency variation, as each note has multiple strings, and the instrument uses a tempered tuning.
The ideal is a single decaying note on a single plucked or struck string, a guitar or dulcimer,say, with any other strings in the instrument damped.
However, even that has issues regarding whether the deck is the cause, as pitch perception can also change as amplitude decreases.
Then, again, there may be artefacts from the cutting process, which are being perfectly reproduced....
So the effect is not necessarily due to the turntable.
John
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