"Hold On, I'm Comin'" (Sam & Dave)

I loved the original Blues Brothers movie (1980) as a kid.  Cable would run it (chopped up and censored, of course), and I'd be there, glued to the set, soaking up every minute.  It's where I first heard Stax soul: Elwood and Jake, driving around in their converted police cruiser, listening to The Best of Sam & Dave on their tape deck.  It made quite an impression on me.
It's where I heard the Sam & Dave track "Hold On, I'm Comin'" (1966) for the first time—a track that never wears out its welcome for me.  Along with featuring the entire Stax rhythm engine (i.e. Booker T. & The MG's + the Mar-Keys horn section), the song boasts the anointed vocals of Sam Moore and the late Dave Prater.  Although Moore and Prater often didn't get along outside the studio, when their voices came together, it was harmony.  The perfect high and low/fire and ice/yin and yang to stir the soul.  There's nothing quite like their blend on the hook: Hold on, I'm comin'...  Pure church.
And I'll even assert that Moore's final verse (When the day comes, and you are down / In a river of trouble and about to drown) is one of the best vocal performances ever recorded.  It's rare to hear that kind of unbridled emotion come through on a studio recording.
Incidentally, I've found that a lot of people don't realize "Hold On, I'm Comin'" was written by Isaac Hayes with lyricist Dave Porter.  (Before Hayes was a star in his own right, he and Porter wrote a number of legendary songs for Sam & Dave at Stax: "When Something is Wrong with My Baby," "I Thank You," as well as the ubiquitous "Soul Man.")
Years ago, I heard Hayes tell Conan O'Brien an anecdote about how "Hold On, I'm Comin'" came about.  And, God bless the Internets, I found the clip on YouTube!
I'll let you watch the video for yourself, but I'll set it up: Stax Records was located in an old movie theater that hadn't been changed or renovated all that much.  Whereas other studios in those days would have had specially-built echo chambers to capture reverb on vocals, Stax just ran mics into the theater's (working) restrooms, which were covered in ceramic tile.  As you might imagine, this made for great reverb on vocals, but maybe a little awkwardness whenever someone needed to use the facilities.
Long story short: Hayes and Porter were working on new music one evening, when Porter excused himself to use the restroom.  Porter was taking longer than his writing partner thought necessary, so Hayes hollered for him to hurry up.  
You might guess Porter's response.

"Walk On By" (Isaac Hayes)

If you like playing "spot the sample" like I do, you'll recognize Isaac Hayes's "Walk On By" as the entire basis of the Hooverphonic song "2Wicky" (1996).  
As with most things, though, the original is better.
Back in 1969, Hayes recorded the album Hot Buttered Soul, which contains his take on the Hal David-Burt Bacharach song "Walk On By."  As music journalist Barry Lazell wrote in the liner notes for Hayes's Enterprise: His Greatest Hits (1980), the label released 27 albums by its entire roster of artists, all at once, in May 1969 as a promotional push--the idea being to get the Stax name and its talent in front of music buyers and radio program directors across the nation.  Hot Buttered Soul was an afterthought--basically a jam session that produced four, sprawling tracks that no one, including Hayes, expected to get any kind of airplay.  The record only existed to help Stax flood the market.  (Lazell points out that Stax's promotional posters had new albums by famed artists like Johnny Taylor, Booker T. & The MG's, and Eddie Floyd, front and center, while the cover for Hot Buttered Soul was tucked quietly into the lower right corner.)
To Hayes's and the label's surprise, the album--particularly "Walk On By"--got major FM airplay and huge sales.  The Motown music machine and Philly soulsters took notice, and before too long, artists from The Temptations to The O'Jays were recording songs with fuzzed-out guitars, heavier/funkier drums, and sprawling arrangements that filled up whole sides of vinyl records.
I'm sure that, at the time, no one could have anticipated Hayes's radical funk/soul arrangement of Dionne Warwick's 1964 hit tune--which is itself a great track.  
It's a pretty radical departure from Warwick's light bossa nova groove.  The drums immediately kick in with massive amounts of reverb, sounding like someone slamming a door and kicking a suitcase down a flight of stairs.  Then there's this extended interlude with lush strings, fuzz guitar, church organ, and fat electric bass before Hayes even opens his mouth to sing.  But when he does sing, you hear this husky, grieving baritone.  Lines like If you see me walking down the street / And I start to cry / Each time we meet somehow take on a different resonance and reveal a deeper pain--especially when paired with the wailing guitar and female chorus backing vocals--than Warwick's version.  It's larger-than-life dramatic.  It's a Memphis soul version of Greek tragedy.

"Do Your Thing" (Isaac Hayes)

There was so much more to the late Isaac Hayes than just being the voice of a cartoon chef on TV.  The man was a pioneer in soul music, not only penning hits for the duo Sam & Dave ("Hold On, I'm Coming," "Soul Man," and "I Thank You") and backing Stax Records artists like Johnny Taylor and Carla Thomas in the 1960s, but also redefining what soul music could be heading into the 1970s.  
He was one of the first soul artists to eschew the radio-friendly single.  Limit a song to 3:00?  Screw that.  He was crafting jams that ran for 10, 15, 20 minutes that sprawled across entire sides of his albums.  
He completely rearranged, reinterpreted, and funkified MOR ballads like "By The Time I Get to Phoenix" and "Walk on By" (look for it later on this list) with a mix of gospel harmonies and rhythms, psychedelic rock guitar crunch, and jazz improvisation--ushering in a new era of the Stax/Memphis sound.
The pinnacle of that sound was the Shaft soundtrack album.  Everyone from your infant cousin to your old-as-Methuselah grandpa knows the title track.  But many have no idea just how fresh it was at the time, or the fact that it won Hayes an Academy Award for "Best Original Song."  That's probably because its once-innovative chicken-scratch, wah-wah guitar (provided by the late guitarist Charles "Skip" Pitts) got co-opted by every greasy composer writing backing music for cheesy cop shows in the late 70s, which had the unfortunate effect of reducing the original to parody.
But beyond the title track, there's a song taking up most of Side Four of the original double album: "Do Your Thing."  It begins simply enough with a soulful horn riff and cross stick pattern on the snares.  But then "Skip" Pitts's fuzz guitar with the tremolo turned waaaaayyyy the hell up slinks in, and you know what you're about to hear is baaaaadass.  
Then, Hayes's baritone comes in with the lyric.  It's nothing too philosophical or groundbreaking, the message being: if you're good at it, if it brings you joy, or if it helps you relieve some pressure (whatever it is), then do your thing.  It's not quite as anthemic as, say, James Brown's "Say It Loud" or even quite as decadent as BT Express's "Do It ('Til You're Satisfied)" from 1974, but it gets the point across.
The vocal portion more or less ends around the 2:30 mark, and thus begins Pitts's raunchy, fuzzed-out soloing.  On the single version, you get about a :30 taste before the solo fades out.  But on the album version, things are only getting started: Pitts solos for 16 solid minutes as the rhythm section locks in to this gangsta lean groove, finally culminating in this psychedelic freakout that includes Hayes blowing kisses into the mic, the children's song "Frère Jacques", and the NBC "chimes"(!) before a needle scratch sound effect brings it all to a jarring close.
It is wild, deep, funky stuff that is worth every one of its 19 minutes.  Classic.