Salam Nura
Thanks for your response.
You said, `living things and non-living things follow God differently.' Thats right.
But echo of anything actually the action of the source, I think, not the action of the reflector.
There must have other bodies like trees, rocks around there. But those were not mentioned in the verse. Those bodies also exalt God, undoubtedly.
Anyway, I agree with your conclusion that `maybe there r ways by which mountains pray that we do not understand or can see!'
Best regards.