Jazz is not Blues and Blues is not Jazz.......

Whatever name you put on them, the debut albums of Van Dyke Parks and (for example) Led Zeppelin are extremely different things. About all they have in common is that they are both music (being generous to LZ ;-). Maybe that's a bad example: Van's Song Cycle has more in common with Classical than it does with Rock.

Now that I've said that: if we consider it acceptable to differentiate between Classical and Rock, why not between Rock and Jazz? Hey, I'm just askin'! But Blues and Jazz? Too much in common to keep them separate.

Good example, @orpheus10. Ray is imo the most important and influential male singer of 20th Century Pop music (along with Hank Williams). Does that sound too "grand"? ;-)

And I consider Big Joe Turner perhaps the first Rock 'n' Roll singer. He too straddled the line separating Blues and Jazz, coming from the Kansas City Jazz scene, but recording the original version of "Shake, Rattle, & Roll" (covered by Bill Haley for the white market). I came to love Joe when I discovered the whole Jump Blues scene of the late-40's/early-50's. Great, great stuff.

Another common denominator between Blues and Jazz is the absolute requirement of being able to "swing". It helps for other musicians, but is absolutely essential for drummers. You might be surprised by how many can’t play a good shuffle (what the swing feel is called in Blues), pure Rock drummers in particular. Not to disparage the dead, but Neil Peart revealed himself as being unable to swing when he performed at the tribute show he put together to honor the recently-deceased Buddy Rich. That’s not me talking Peart fans, that was a number of other pro drummers after the show.

One guitarist who can play both very well is Robben Ford. He was living in San Jose for a while in the early 70's, and I used to see him live regularly (the bassist in my senior year high school band was playing bass in The Charles Ford Band, named after Robben and his two brothers'---also in the band--- dad). Robben later joined Charlie Musselwhite's band, and later Miles Davis himself. Musselwhite and Miles---as Blues and Jazz as you can get, and very different from one another.

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 ;-) .