You want a nice sonic overload, Gregorian chanting while simultaneously playing Sunn O))) is a fantastic sound wall with some doomy undertones and heavenly chants.
Some songs work better than others but on the whole most of their work doesn't have a beat so there's no mixing you need to do to make it all just work.
Could probably go full binaural beats with it if you really wanna tickle your brain...probably something in the theta range...
