This track is A 12 bar Blues in G minor.
The turnaround at the end uses both the 6th chord (Eb) the 5th chord (Dm) and also the altered 5th chord (D7#9) for extra filth before the form starts again.

It was made using Nanostudio for the iPad, while I was on a ferry beside some drunk truckers.

12bar blues exercise Gm improv jam lead guitar minor nanostudio pentatonic