The Real Folk Blues, album titles of both Muddy Waters and Sonny Boy Williamson. I think of that "hybrid" genre designation in terms of rural, acoustic Blues. Before the southern blacks moved north, plugging their new electric guitars into small combo amps, in order to be heard above the din of the audiences in the big city bars they were now playing.
The obvious connection between Blues and Jazz is that is was originally predominantly performed by blacks. Jazz requires a more advanced degree of technical proficiency to be performed properly, at least imo. The musical structure of the songs of the two genres are very different; lots of Jazz is performed over long periods of no "modulation"---no chord changes, just improvising over one chord. It is the interaction between the musicians---the musicianship---that is the focus of the music. Other Jazz has very sophisticated chord structures, modulations, and arrangements (think Ellington and Basie).
In contrast, lots of Blues songs have the traditional I-IV-V chord progression, with more formal song structures than lots of Jazz. An intro, 1st verse, 2nd verse, chorus, guitar solo over a verse chord progression, repeat the first verse, chorus, outro. Or a variation on that structure. Not all, but lots. The first time I saw the following (maybe a year before their first album was released), they were named The Steve Miller Blues Band. Boz Scaggs was just the band’s rhythm guitarist, playing chords on his Gibson ES335.
We white suburban (San Jose, CA) kids were first exposed to Blues by The Paul Butterfield Blues Band in ’66, so the English Blues/Rock bands that followed (Cream, The Jimi Hendrix Experience, Led Zeppelin, Fleetwood Mac) didn’t sound like real Blues to me. It sounded like a pale imitation, sort of like Pat Boone covering a Little Richard song. No offense, lovers of Cream, Hendrix, Zeppelin, and early-Fleetwood Mac fans ;-) .
