I am still looking for a very low sound. By deep I think I mean resonance. Perhaps the wavelength. would be dark blue. Tags may include cavernous.
I think I have heard similar sounds/tone in tuva or inuit overtone singing, maybe gregorian chant, a cello, a sound effect from war of the worlds.
Would you have a particular cello part in mind? If you were to write one, I would be glad to play it. Or at least try to play it .