The Prelude in C Major, BWV 846 is the first prelude of the first book of the Well-Tempered Clavier of Johann Sebastian Bach.
This is by far the simplest prelude. It is easy to read and has no technical difficulty with the rhythm. However, it is hard to memorise it because it’s the same pattern that is repeated in each measure but in other tones. Although it is in C major, it has many alterations.
It is therefore affordable for a beginner but it takes years to play it correctly and bring it to life.
It was by playing this kind of song that I really felt the difference between my digital piano (a Yamaha CVP 503) and my grand piano. The more precise sensitivity of the acoustic piano allows a much more emotional interpretation.
EDIT: Today, with a good digital piano (Kawai CS8) plugged in midi on my mac and good VST’s, or with my Korg Kronos II, I can get as good results as on my acoustic.