If you copy a noteblock while holding Control (which copies the NBT data) it won't copy the note it's playing. Because of this, you need to manually set them to the right note. I didn't do much research about it, but i know that 1.21.4 is affected (I'd guess it affects all the versions with copying NBT data).
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We're tracking this issue in MC-136932, so this ticket is being resolved and linked as a duplicate.
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Duplicates MC-136932 🙂