Q: What do the colors and sizes of the bars indicate? A: Each instrument has a different color; the solo instruments have brighter colors; the non-solo instruments are wider (taller) to indicate that more than one instrument is playing each note.
Q: Who is playing this? A: The solo violin parts are performed by Lara St. John and Scott St. John; the orchestra is New York Bach Ensemble, under the direction of ???.
Q: I hear a harpsichord, but I don't see it. A: True. The harpsichord is not included in the score; it is usually improvised. To include it in the animation, I would have had to have transcribed it, which would have been more trouble than it was worth. Anyway, you are seeing all the notes Bach wrote.
Q: Did you already upload this? A: Yes, but I ran into copyright issues with the previous one, and decided that it was simpler to re-do it, using a new recording with more explicit license terms, than to try to straighten out the mess with the old one.