Moon Io orbits Jupiter 4 times as fast as Ganymede. Europa orbits 2 times as fast as Ganymede. This is a kind of "orbital resonance." (Moons not to scale but orbital ratios are exact) Lines connect moon pairs at regular time intervals. Set moon pairs to 1 for just Ganymede to Io. Set to 2 for Ganymede to Europa also. Spacebar erases lines. We make pairs of musical notes play when pairs of moons align (when they have the same angle). The notes are octaves apart. The highest note is for Io and has twice the frequency of the note for Europa and so sounds one octave higher. Europa's note has twice the frequency of Ganymede. This is to bring out the analogy between the doubling of orbital frequencies and musical frequencies (once called the music of the spheres). You can adjust "speed" but the ratios of the angular frequencies of the moons will remain 1:2:4. Moons sizes are not to scale. Distance to Jupiter is not to scale. "p" key for polar view of Jupiter, "s" for side view.
I added a orbit counter between ganymede and europa since io will never be equal to the other moons.
