The head is split between two and four, and contains alternate chords and stop rhythms. The Gm chords are made more interesting by having the extended notes in the chords move down.
The blowing changes are in straight-ahead four. You specify how many solos you want by changing the "4X" under the last Gb7, after which it goes back and plays the head.
I find this a lot of fun to play and improvise on.
Here is a version of Bye Bye Blackbird as played by Keith Jarrett. A very good transcription (by Michael Lucke) can be found on Youtube. Cheers, Norbert