I don't know enough music theory to know if it fits the definition of downward modulation, but upon reading your question I immediately thought of Portishead - Glorybox
That is a very cool sounding song, add it to my collection.
I don't know or think it actually downward modulates in the sense of it getting lower in the key sense but it definitely has a descending chromatic chord progression, I believe. But my music theory is also rusty so if some music-person wants to clarify have at it
Might do a seperate question just for that, maybe make it a series