Bach's Preludes and Fugues from the Well-Tempered (i.e. equally-divided-octave tuning) Clavier (keyboard instrument) comprise two volumes (each of 24 pieces) of a prelude and a fugue in each of the twelve major and minor keys.
The first volume of WTC is generally fresher, more varied in style and substance, and more spontaneously-fluent than the second - and I prefer it.
The above prelude is an example of why I love WTC Volume 1. It is a short, simple, two-part 'invention'; making considerable use of 'perpetual motion' semi-quavers in the bass, to drive a melodic line that transcends its typically baroque-era use of sequences to combine (or alternate) joy and yearning-pathos in a deliciously bittersweet fashion.
It also represents very lucidly what is special about Glenn Gould, because this two-part texture lets the listener hear everything that is going-on; in terms of the crisply-detached separation yet subtle phrasing of each individual note - even the decorative flourishes; and the over-arching shape and mood that Gould creates.
In other hands, this tiny piece can seem merely pleasant - even trite; but Gould's musical concentration and insight raises it to a level that has given me repeated happiness for the past 44 years, and counting.