@Dog_Faced_Boy said:

I'd be curious to get your take on earlier periods of Phish jamming, specifically '92 - '95. While the band did modulate jams at this point, it seems to me that a bigger aspect of the jamming back then compared to '97 thru to now was rhythmic changes.

I also hear a lot of jams, especially prior to 1993, being led by what's known as sequencing. This is when you take a melody, or more often a short melodic "cell," and repeat it more or less in the same rhythm and style but at a different pitch level. This is especially relevant and interesting because sequencing is one of the stock techniques of Phish compositions (I'm especially thinking of the opening to "YEM," the second composed part of "Bowie," a ton of the Rift album). So Trey is taking a technique that he uses in composition and applies it in improvisation. It's very cool, and very much in line with a band who is still mostly following a leader (Trey) since he can move the jam around sequentially and the rest of the band just follows, or holds down a pedal to create dissonance. My favorite example of this is the 5/9/92 "Tweezer." It's all sequencing.