Some info from David Lemieux: "That November 68 tape is not in the vault as far as I know, and I went through everything from Fall of 1968 a few years ago. I know the session, though, and am quite certain it's TC learning the material."
I'll add that a date of November (or earlier) wouldn't rule out TC - he could have visited the Dead in the studio while on leave, as he did when they were recording Anthem. Considering his work on that album, it makes sense he'd be first choice to work on the Aoxomoxoa material as well. It would also partly explain why he sounds so cautious & unfamiliar with the material, as he might not have played any of it before that day. So that's something else to consider. As a sidenote, there's an interesting development in the 9/21/68 studio jam I mentioned. Lemieux mentions that there were two other guitar players (on one track of the recording), listed only as "David and Vic." Gans suggests that one of the players is David Nelson, but I don't know who Vic is. (The brief jam included on the Taper's Section seems to be just an excerpt from the start of the session.)
