Did you know that the man has some guitar lessons online? I did not. They are invaluable. Let him show you how it’s done.
https://youtu.be/AVe24YFGoiM
BB’s technique has some idiosyncrasies. He holds the guitar neck like an axe handle, which you aren’t supposed to do because it impedes your ability to move around the neck. But as BB himself points out, getting a lot of notes out in a hurry is not his style. Hooking your thumb like he does give your hand more strength and stability, which is what you want when you bend every single note.
BB also doesn’t alternate his pick direction like you’re supposed to. Instead, he starts his phrases with an upstroke and then plays the rest on downstrokes. I guess this is to take advantage of the slightly different timbre each pick direction gives. This too limits his speed, but BB knows that you don’t have to play a ton of notes if you just play the right ones with the right sound at the right time.
The best part is when BB gets to his use of blue notes. He talks about how he doesn’t want to nail the 5^ dead on, he wants to bend up to it, or almost up to it, or slightly past it, all three of which give an otherwise boring scale tone a broad range of new colors. When BB bends his ♭3^ up toward 3^, he very deliberately doesn’t quite get there. The pitch he lands on is the blue third, a microtone in between the minor and major thirds. BB also bends ♭7^ toward 7^, but once again deliberately stops short of it to get the blue seventh. You see the terms blue third and blue seventh used all the time by music theorists to refer to ♭3^ and ♭7^, but this is wrong. The blue notes are between the piano keys. Every competent blues guitarist knows this, though they they don’t necessarily know that they know it.
BB tries to explain the need for all of his pitch inflections here:
https://youtu.be/TA-zCK0dEds
The interviewer points out that just about every note gets some pitch inflection. BB relates it to speech, how pitch inflection begins and ends sentences, how it commands our attention. He doesn’t verbally articulate what he’s doing very clearly, but his playing says it all.
Gerhard Kubik has a theory that the blue third and blue seventh originate in traditional tuning systems from West Africa. One such tuning system is equiheptatonic, meaning that you divide the octave into seven equal parts, rather than the twelve parts we use in Western equal temperament. The “third” you get from equiheptatonic tuning is right in between the equal-tempered minor and major thirds–the blue third. The equiheptatonic “seventh” is in between the equal tempered flat and natural sevenths–the blue seventh. I have no idea whether BB King is aware of equiheptatonic tuning explicitly; it’s more likely that it’s an idea that was passed down aurally from his enslaved ancestors, and now he just knows that it sounds “right” to him. And not just to him! Every blues fan loves blue notes, though we rarely know explicitly what we like about them.
My love for the blues was a purely instinctive one for many years. It’s only recently that I’ve tried to actually figure it out analytically. I find it inspiring to discover that descendants of enslaved Africans managed to protect so much of their musical culture from centuries of brutality, and that it continues to thrive below the radar of “official” music culture.
Now I’d like the learned music community to do some better learning, to recognize that Europe isn’t the only wellspring of Western harmony, to acknowledge the bigger and richer musical world out there. Pop musicians and fans figured this out decades ago. But it’s hard to find a music theorist who talks about the blues at all, and it’s even harder to find one who does so from a place of real understanding. This is a situation that I’m working hard to amend. Fortunately, we have ample documentation of the music itself. As long as we trust our ears, we can wait for the academics to catch up.