Ambient downtempo is the genre exhaling, the point where the beat stops insisting and becomes weather.
Eno's Music for Airports drew the map: music as deliberately ignorable as it is interesting, built from long tones and space.
Downtempo's ambient wing keeps a faint pulse, a dub echo, a half-time kick, so it drifts without quite dissolving.
It's music for the end of the night, or the start of a slow morning: harmony moving at the speed of light through a window.