Several things occur to me. One is that I completed the "Ultimate Blues" cited above:
I didn't wake up this morning...
Didn't get out of bed.
But when I didn't miss my baby,
I knew that I was dead.
Didn't have no coffee,
Didn't look down in my cup;
Didn't say, "Good Morning" to the blues,
'Cause I never did wake up.
Got those never-no-'mo,
I wrote this with some other people, and there are more verses, most of which are puns ("didn't end the day bein' dead-drunk/'cause I started it bein' dead" is one example).
But the shortest song I know is (to the tune of "Jealousy"*):
Entropy! Why mussst there ... ZZZ-ZZZ-ZZz (sung in a nodding-off fashion)
Joe Hickerson used to sing one that went,
Come back with my wife, you horse-thief!
* There is a parody of this song called, "Leprosy," which I think I had in mind when I wrote "Entropy."