Bach, Passacaglia and Fugue in C minor, BWV 582

Passacaglia and Fugue in C minor, by Johann Sebastian Bach, performed and visualized by Stephen Malinowski. FAQ Q: What do the colors mean? A: The colors indicate different melodic lines in the piece. The part for pedal (the lowest part) is always violet, and there is one stop (starting at about 4:55) that is always blue, but the rest of the colors just indicate different melodic strands (and don’t correspond in a consistent way to anything in the score). Q: What instrument is this?