That Kool and the Gang track is stunning. A couple of the chords are the same as Donny Hathaway’s ‘Little Ghetto Boy’ and, by extension, Dr Dre’s ‘Lil Ghetto Boy’, but those tracks are too tense to fit this thread's criteria.
Is effortless slickness a prerequisite for smoothness (something that's self-consciously slick, like Jamiroqui, doesn't make the cut)?
One definition of airy is "giving an impression of light gracefulness and elegance". Does this apply to smooth too?
Start at 3.42: