I think one of the reasons blues has a little better definition than "folk" is that it is a musical form (usually eight bars of lyric over 12 bars of instrumental, tho' that can vary considerably and there is a 16-bar form) that is as identifiable as certain other forms — jigs, reels, etc. spring to mind; my understanding of those is that they're defined by the rhythm patterns.

But then things start to get muddy. John Hurt is generally tho't of as a blues man, but he played a lot of other things too. So did Mance Lipscombe, Leadbelly, Blind Boy Fuller, Bo Carter and just about every other blues great you could name.

But then you could bring in the "feeling" argument — that it's not the song or the form, but the emotion it conveys. Trouble with that is that there are songs in blues form that run the entire range of conditions/emotions.

As for the rock/blues and jazz/blues cutoff lines, it's every man for himself on where you draw the line. Personally, as soon as they start adding synthasizers, screaming electric guitars, screaming vocals and too much drum, it's crossed the line in to rock. Jazz is a little harder to pin down, so I don't have any real clear line of demarcation on that.

And all that said, I usually come full circle and agree with definitions like "blues ain't nothin' but a good man feelin' bad" and "blues is just a good woman on your mind."

Besides, I have to go to work now.

cheers,

david