Courtesy of Mr. Freddie King, the Texas Cannonball from Chicago
I like these notes a lot. I think of this as being in a C minor pent with added A and D. That seems to be the way this lick is generally used, in a C minor pent context. The earliest I have heard this lick is by Freddie King. It also shows up in other guitarists' work, such Elvin Bishop and Walter Trout (he uses it a lot). Probably mid-60s Clapton and Green, oh yes, B.B. uses it, too. Definitely not Albert King, who is more of a straight minor pent guy when doing 12-bar blues. It can be used on C7 in a C 12-bar blues, but also over F7 and G7 if you have a more expansive harmonic view. I like to play ahead of the chord as an anticipation of the coming harmony.