In “The Ballad of Frankie Lee and Judas Priest,” “creep” rhymes with “leap,” two nicely juxtaposed contrasting movements.  It’s “creep” that finds “midnight” in front of it though, not leap, which would make the lines with that rhyme less open to interpretation:

Well, up the stairs ran Frankie Lee
With a soulful, bounding leap
And, foaming at the mouth
He began to make his midnight creep
For sixteen nights and days he raved
But on the seventeenth he burst
Into the arms of Judas Priest
Which is where he died of thirst

Really, it’s the word “make” that causes interesting problems.   A person can make a low to the ground movement, because he would rather not be noticed.  So “midnight” describes the time of the creeping.  And this makes sense in the song, being that this is no home but a brothel Frankie Lee goes to (creeps) for sixteen nights . . . days, too.  But Frankie may have turned those days into nights (“moral desert,” Robert Shelton calls it), succumbing to temptations of the flesh.  So Frankie Lee may have made his midnight go slower, move gradually, to the tune of 16 days worth of midnight.

Not sure if anything is revealed by this; even the little creep who carries Frank Lee’s body to its grave concealing his guilt while doing, says, “‘Nothing is revealed,’” just what someone who creeps or a creep would want, perhaps especially around midnight.

Here’s the audio of Bob singing it live in Portsmouth in 2000 sometime within 24 hours of midnight: