so, I've wondered why I couldn't sound like some of the blues guitarists I listen to. I call this genre nightclub blues: BB King, Son Seals, Luther Allison, etc. There was something in their songs I just couldn't seem to imitate, even at a lower, beginner's level. I had my 7th chords and the minor and major pentatonic scales, but it wasn't the same. Adding the major pent certainly helped to sound more like BB King, but still I wasn't there. So in this week's lesson I asked my guitar teacher about minor blues (among other things we discussed). He played a I-IV-V in minor 7ths, and there it was. I played minor pent over those chords and I got that "nigthclub blues" sound -- more mournful, more soulful. That's what I was missing. It was the rhythm guitar, not the lead.
so of course now I'm working every day with minor 7ths and trying to put together some rhythm/lead switching so I can approximate it in one guitar.
Rhythm guitar is so important in blues, I'm finding out. It's equal with the lead in many ways. the lead by itself is sort of out there, somewhat skeletal. It needs the muscles and bulk of the rhythm to play against, for color. that's why you gotta learn about minor 7ths, power chords (5ths), 6ths, 9ths, etc. The same lead played over these various chords will create different songs.