[BabyGiraffe]

Hello,
Is it true that old pianos were tunned half a note lower, that what today sound as D sounded before as D#? I ask that because if that is true, the most of the classical pieces are supposed to sound half step lower.

Thank you

There was no standard, so noone knows how most classical pieces could have been tuned.
https://en.wikipedia.org/wiki/Concert_pitch#History_of_pitch_standards_in_Western_music