As I'm sure you're aware, restless leg is an odd "itch" that can only be "scratched" by movement (for lack of any good words to describe it). The movement isn't compulsory, but the discomfort becomes overwhelming without it. I suspect the sensation is there all the time and not just at night, but there are enough other stimuli during the day to drown it out. The brain.fm music seems to have been effective for the same reason, providing a welcome distraction from the sensation.
Restless leg is supposedly a mineral deficiency, but my blood work comes out normal, and supplements haven't been helpful. Up until now, the only remedy I've found is working out in the middle of the night, which replaces the restless sensation with a tired-from-exercise sensation. This only works if I can fall asleep before the exercise wears off. The brain.fm effect is less powerful than exercise, but doesn't have a time limit for falling asleep. I wonder if this is unique to brain.fm, or if it would work with any other type of music.
Besides distracting from restless leg syndrome, the brain.fm music was quite relaxing (more so than ambient or nature music normally would be). I did notice the 3D effect, and wondered what that was about. There is clearly something going on here, but I don't have the knowledge or tools to say what. It sounds like your EEG sleep studies have done just that, so thanks for mentioning those. I had no idea it was so measurable.
This would be worthwhile it if the results are as good as you say they are. I've gone ahead and purchased the headphones - for science! Thanks for the offer, and for your epically-long reply. This type of thing is fascinating to me.