Well, I can tell you that is most definitely (the 80s version, now) NOT plain ol' E. I used to think it was. My keyboardist, MTTOURPRO, showed me how I was incorrect. Play in straight E along w/ Without A Net. You will find many instances where it just doesn't fit. I THINK (and I'm still trying to get used to it) that it's Esus4(add9). SO, on guitar, that's more easily translated into F#m7 with an E in the bass. NOW, listen to Garcia - the mfer adds a F note in there to make it spacey!! So, you can really run a funky scale in F#m7 (make sure not to lead with the F# note, as it's really over an E bass), but adding that F in there is pretty cool! OR, you can run an Esus4 scale with both an F and an F# in it!!!
As I said, I'm still working on making it sound right.
NOW, as was stated earlier, once you run through that big bulk of the jam, you shift up to an F# for 4 measures. THIS F# is a MAJOR scale....then you go back down to that F#m7/E jam for a while longer (we jam it out some more, not 4 measures, but not as long as the first bulk of the jam), then all shift back up to F# for 4 measures, then up to G# (again, in a MAJOR scale) for 4 measures, then the seabirds fly.....
"Once in awhile, you can get shown the light in the strangest of places, if you look at it right." - R. Hunter
"If we had any nerve at all, if we had any real balls as a society, or whatever you need, whatever quality you need, real character, we would make an effort to really address the wrongs in this society, righteously." - Jerry Garcia