I play piano and watching videos of Gould playing is fascinating. He violates every rule your piano teacher tells you about performance, from his unusually low chair made to accommodate a back injury to his habit of singing along to tunes that was often picked up in his album recordings. I especially like this performance of Beethoven's 32 variations in C minor by him [1]. [1] https://www.youtube.com/watch?v=UoWXRlw9…
https://www.youtube.com/watch?v=SvWPM783TOE
He was so insistent on his own interpretation, that even one of the best regarded conductors in the world couldn't convince him otherwise. After many years the "unusually" slow tempo doesn't sound so extreme, and to me even preferable. Glenn Gould was incredible in terms of his musical understanding. Maybe that's why his Bach was phenomenal because he could bring out the multiple layers as much as he liked, and even improvising new voices in his humming at times.
If anyone is interested in Brahms Piano Concertos, I also recommend Gilels' performances, which remain the best in my mind: