BWV 847 from the WTC is almost like a practice piece but Gould makes it sound interesting.

https://www.youtube.com/watch?v=L7AQtLnNZOY

Here is a comparison on BWV 974 (Adagio)

https://www.youtube.com/watch?v=c2gVYB5oZ7o (Víkingur Ólafsson)

https://www.youtube.com/watch?v=C2zix8yTY_Y (Gould)