Watch the Major or Minor Blues online guitar lesson by David Santos from 50 Bass Grooves You MUST Know
This is a 12 bar blues. The bass line uses a half step approach to the root even though it is a flatted 7th in the chord of the moment. We are using a major seventh note against a dominant 7th chord which contains a flatted seventh. The half step approach is so strong though that it overrides the fact that the chord of the moment contains a flatted 7th.
It sounds completely normal.
There is an anticipation to the five chord in this 12 bar blues.