I wanted to come back around to this and let you know that I was so intrigued by the Solfeggio Harmonics that I ended up buying both sets. I've been listening to them and have found them really powerful as a boost to meditation. Three of them in particular seem to take me right into the zone.

There's one I can't bear to listen to (it has Tibetan throat singing in it and that sound just freaks me out).

I have a long history with binaural beats (which are embedded into these recordings), and I suspect that those are where the power lies, more than in the wash of musical sounds. I've been using Bill Harris's Holosync for years. It seems intuitively obvious that not everyone's brain frequencies would be identical, so maybe I just lucked out on these particular sets of sounds.