"I Feel for You" (Chaka Khan)

I remember when Chaka Khan's "I Feel for You" came out in 1984.  It was the weirdest sounding thing I'd ever heard: there was Melle Mel from Grandmaster Flash & The Furious Five rapping/chanting Khan's name, a sample of "Fingertips, Pt. 2" by Little Stevie Wonder thrown in for good measure—not to mention a live Stevie Wonder, playing harmonica on the track, and then odd tape noises and random effects that kind of left you wondering if someone had leaned on the wrong button during the final mixing.  I listen to this song now and marvel that anyone had the guts to even attempt anything so bizarre (much less that mainstream radio programmers had the stones to play it).
Because Khan owns her performance so completely, a lot of people don't realize the song actually is a Prince composition.  It originally appeared on his 1979 self-titled album, albeit in a much leaner format.  In fact, compared to the late mega-producer Arif Mardin's everything-and-the-kitchen-sink production for Khan, Prince's original sounds almost like a demo.
In truth, Khan's cover of "I Feel for You" came about because her record company had expressed "concern" that she'd released several albums in a row without a definitive hit single.  (In record company speak, that means, "We're dropping you soon if you don't get a hit.")  So Mardin specifically set out to create something attention-grabbing that felt very futuristic, combining the Uptown vibe of hip-hop with the Downtown vibe of electro-pop and adding the element of soulful R&B.
Mardin recounted to NPR's Michele Norris in 2005 that the idea of using Khan's name as a rhythmic element came out of a conversation with Khan's brother, musician Mark Stevens.
"I said, 'You know, you have two sisters—one of them is called Taka Boom, and the other sister is Chaka Khan. Why can’t we use these two names like percussion? Taka Boom-Chaka Khan-Taka Boom-Chaka Khan'.”
Even though the initial experiment didn't quite work, it did establish the groove for the song, and the vocal percussion idea morphed into Melle Mel's rap.
Mardin also revealed that the famous Chaka-Chaka-Chaka-Chaka Khan "stutter" at the beginning of the song (a technique that hip-hop producers jumped on and ran into the ground in the years that followed) was a serendipitous error.
"As we were mounting the recording onto the main master, my hand slipped on the repeat machine.  And we said, 'let's keep that; that's very interesting'."

"What Cha' Gonna Do For Me?" (Chaka Khan)

Chaka Khan could sing her damn ABC's, and it would be a hit.
But give her the right context, the right song, and the right producer, and she will create a classic every time.  "What Cha' Gonna Do For Me?" from the 1981 album of the same name is a perfect example.  Here, she had a song penned by Hamish Stuart of Average White Band plus superstar producer Arif Mardin (who had a golden touch for bringing out the groove or soul in any track) at the helm.
Every element of this song is in its right place.  Chaka's lead and backing vocals (as always) are on point.  The twin guitars are playing these tasty, dueling riffs, split into separate channels for maximum rhythmic effect.  There are synths that strategically underpin parts of the track, but they're tastefully used.  (The same can't be said for a lot of other R&B tracks of this era, which overused synthesizers.)  And then the legendary Steve Ferrone (who has been full-time drummer for Tom Petty & The Heartbreakers since 1995) locks in this funk groove, a millisecond behind the beat; it's the same way the late Al Jackson, Jr., from Booker T. & The MG's used to drum: just behind the beat, but as consistent as a metronome.  It's a technique that gives the track a swinging, funky feel.
Also, I'm typically not a fan of keyboard bass.  It always sounds a little wan and cheesy to me compared to electric or upright bass.  But everything else on the track is so organic--including how the drums are miked (you hear the perfect separation of the hi-hats and ride cymbals in each speaker, the way you would hear them played live)--that the keyboard bass not only is passable, but it lends a nice little thump and another layer of texture to the whole affair.  (In actuality, there's electric bass on the track, too.  It's most prominent in the breakdown around the 3:12 mark.)
Just a great, feel-good groove from Queen Chaka.