I shall try to memorise that sequence and think of it as The Owl Call Sequence from now on. It may be expressed as: I7 - IIIbo7 - IIm7-5 - I.
I wonder whether it occurs at the start of any other tunes. Can we think of one? I doubt it.
You can listen to Tuba Skinny playing Owl Call Blues, with Erika singing, BY CLICKING ON HERE. And you can read what I wrote some months ago about Owl Call Blues BY CLICKING HERE.