Of legendary status is the 1981 studio recording of Glenn Gould performance of Bach’s Goldberg Variations. It is a piece for solo piano, consisting of an aria + 30 variations. In the musical world, variations is a compositional technique where the composer takes a musical idea/theme and alters it in some particular way in each variation. These can be changes to, or variations on melody, harmony, composition, counterpoint, and so on.

Bach’s Goldberg Variations revolves around the bass line and chord progression introduced in the Aria. One can refer to the skeleton of the structure of harmony here: [Form of BWV 988]
Along with the score of the variations (download here), one can see that the harmony from variation to variation follows true to this skeleton–even though the rhythmic and melodic material change each time.

Glenn Gould’s interpretation of the set is wonderfully light, refreshing, clear, and raw. The clarity with which one can follow all the melodic lines woven together is something to strive for, not only in this piece, but in Bach’s Well-Tempered Clavier (Fugues, especially) and Inventions as well. Once again, I have linked a recording in which one can study Gould’s technique and way of achieving such tone. That being said, I would like to add this warning to the ambitious who may want to emulate Gould’s piano technique:

The height of one’s seat at the piano is determined by the position of the elbows, which should not be below the level of the keyboard to avoid introducing too much weight into the playing. Sitting much lower prevents the pianist from using the weight of his upper body. (I am convinced that Glenn Gould was able to play the way he did not because of his abnormally low sitting position but in spite of it. It certainly has not worked as well for some of his emulators.) People with a small build in particular may need every ounce of their upper body weight to produce a powerful and full sound. On the other hand, sitting too high may invite shallow playing, with fingers not reaching to the depth of the keys.
–Boris Berman, Notes from the Pianist’s Bench, pg.30

That being said, Watch and Listen on! Best done in a quiet room, in a quiet mood. For the uninitiated, a second warning: Glenn Gould is a character; among many of his odd habits, ‘humming’ and ‘hurring’ along while he plays is common.

J. S. Bach – Goldberg Variations
00:00 – 06:34 Interview with Glenn Gould
06:34 – 58:56 Goldberg Variations