My freshman year at Northwestern, one of my first assignments from Rex Martin was one that didn't involve my tuba. He wanted me to get deeper into the interpretation of music and told me a good place to start was with renowned pianist, Glenn Gould.
His assignment was for me to listen to different versions of the same piece by the same performer. That piece was the Bach's Goldberg Variations for solo piano with the aforementioned Glenn Gould the performer. His two recordings of this staple of the piano repertoire are both industry standards that have withstood the test of time and many consider them the finest piano recordings ever made.
What is truly stunning about them is how different they are from each other. The first features a 23-year-old Glenn Gould in 1955 playing fast tempos and quite aggressively in spots. The second is of a 49-year-old Glenn Gould in 1981 playing much slower, more reflective tempos. In fact, the 1981 recording is over 12 minutes longer than the earlier one!
The other part of my assignment was to listen to them both while following along with a score. Mr. Martin wanted me to listen specifically for the balance between all of the harmonies relative to the melody throughout both recordings. He also wanted me to listen for specific differences and how they affected the musical storytelling.
It was a truly remarkable experience for me that I recommend everyone try. Here are the two recordings on YouTube followed by a link to the publicly available score. I really owe Rex Martin one for making me do this exercise at a young age. Actually hearing and analyzing these two contrasting examples by Glenn Gould was more valuable than listening to 10 masters talk about interpretation.
Thank you, Mr. Martin!
1955 Version (23 years old)
1981 Version (49 years old)