This Miles tune is a simple "almost" blues. It is mostly the familiar 12-bar pattern, but notice that the song form is a double-chorus. And most importantly the first chorus does not end up on the root chord.
The song is in Bb concert, so you would expect bars 11 and 12 to be some flavor of Bb, but instead that first chorus moves down to Ab7. The soloist (and band) must keep track of the even and odd choruses to make that distinction on the even choruses.