"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.