I will just reproduce what I just came across in a late 1972 discussion of the Grateful Dead, probably by a college undergraduate music major, who had seen all of two Dead shows. I post it on AHATT principles.
Perhaps the best recorded example of what may yet be another turn in style, and one which was embryonically apparent in at least two of the Dead's latest concerts (Philedelphia [9/21/72] and Washington [9/20/72]) can be found in a largely undiscovered album Garcia recorded with Howard Wales called Hooteroll?. Without a doubt, Garcia's collaboration with the superb blues/jazz organist, Wales, will continue to produce dramatically important results.
To a large extent, the Dead's recent dream-like style of playing, characterized by slowly evolving, minutely subtle melodies which at times are intentionally shattered ... by powerfully syncopated chords and notes, by Lesh's imitation and by a general accelerando, can be attributed to Garcia's experiences with Wales on Hooteroll? It seems likely, too that the increased influence and often outright performance of jazz preeiminently displayed throughout much of their latter concerts can be developmentally traced to Hooteroll? as well.
Now, this guy could just happen to have listened to Hooteroll? in writing up his review (or preparing for the show, or whatever) and could be following the law of the hammer. He might not know what he is talking about. Maybe Jerry had an underlying interest in jazz which led him to play it with the GD and Howard (spurious correlation, plausible). Maybe Jerry's jazzy work with the Dead influenced his style with Howard (reverse causation, highly doubtful). I don't endorse Rob Pritchard's sentiment. Because I find GD-GOTS crossovers to be really useful to parameterize, I merely note it with interest and pass it along.
Pritchard, Rob. 1972. Grateful Dead Resurrect Country, Blues, Jazz. Cavalier Daily (University of Virginia), October 6, 1972, p. 2. Accessed via Google New, though I can no longer find it there. The Cavalier Daily appears to be archived on line, if incompletely. A google search turns up this issue, but I can't seem to access the content.