The drums are used to outline the three roots in a blues progression. The melody over top uses a weird scale that resembles harmonic minor with a raised fourth degree. If there's an official name for this scale I'm unaware of it.
The song starts off and ends in G. Each soloist plays in a different key; Dmi for piano, Emi for horn and F#mi for alto saxophone. I added some simple backgrounds to frame each solo.
Check out Alex Gertner on that French horn! Go Alex go!