Scott Joplin's closing material in "Pine Apple Rag" sounds like an itch that you can't quite scratch because you've been in a coma for 68 preceding measures and are now in an uncomfortable public situation and you can't get away to scratch yourself silly. Joplin uses a flat VI in measure 77 to create tension, which he only intensifies by creating a thick texture, doubling the root and the fifth in the right hand- what a drama queen. Joplin also resolves the flat VI to a I64 chord in measure 79, but uses an f natural embellishment to keep the tension alive before moving to a IV7 in measure 81, Joplin now emphasizes the f natural even more by placing it in the top voice. He finishes measure 81 with a minor iv, but you know that there's more material coming because of the f natural which leads to the I64 in the next measure. With the arrival of the V64 in measure 83, as a listener, you're relieved, thinking it will be over the minute tonic comes to the rescue. Much to your dismay, Joplin just teases you with his first ending going to tonic but using that f natural to lead into a repeat of the section.
At this point, the f natural feels like a wool sweater on your bare skin in mid-July. You're sweating, itchy, and having an awkward conversation with overly friendly relatives you've never met and who happen to be Michael Bolton fanatics. Somehow, you just can't end the conversation and make a clean escape. Joplin's mixture chords are those relatives, and the recurring f natural- that's your wool sweater. You sit through one more repeat of Joplin's closing knowing that with each f natural comes another rant on how wonderful Michael Bolton's rendition of "When a Man Loves a Woman" is. When the relatives finally go home and Joplin ends "Pine Apple Rag" with a perfect authentic cadence, you run screaming to your air-conditioned room, rip off that wool sweater and find your hairbrush so you can give yourself a good scratching in front of the breeze. After all those hurried mixture chords and embellishment, it feels pretty good to hear the familiar dominant-tonic arrive.
If I were a talented enough pianist to play this piece, I would accent the downbeat of measures with mixture chords such as the flat VI just to let listeners know that they're in an awkward situation with these relatives and in a pretty big hurry to get the visit over with. I would also try to emphasize the f naturals which would hopefully give the listeners the same idea I have: the constant teasing by prolonging harmonies or leading to more material feeling like the wool sweater you can't remove. I would also take into consideration Joplin's voicing. Why did he use such a thick texture on those mixture chords? I hear it in the sense that he's trying to create some immediate, hurried discomfort that will not be resolved any time soon- you have to wait until the second ending to get the true, undisturbed tonic.