I suspect the overtones you get with brays are ridiculously similar to those of a mildly overdriven electric guitar. I have a bray harp (not proficient on it by any means) and it plays a mean “Ironman” / Black Sabbath riff. Not sure that’s what you were looking for.
But for mysterious/contemplative early music, my one-stop-shop must be Anonymous 4, if you’ve heard of them?