Attention classical fans - question about Well Tempered clavier - Glenn Gould

[Bubbajazz]

I recently picked up a copy of Glenn Gould's recording of WTC book 1. I am enjoying it immensely, but have a question I am hoping someone here might have the answer to.

 

There is something odd about either the recording itself or the piano tuning, or my ears have gone totally haywire.

 

I have perfect pitch. I also know several of these pieces from playing them myself.

 

Basically, many pieces on the recording sound like they were transposed up a half-step to me. I don't mean the actual pitch - I mean the tuning. Have my ears finally betrayed me, or is there something going on with the tuning that I wasn't aware of? Any info gratefully appreciated.