I think the confirmations that this is TC are clinching. It's a little-practiced TC, though - this tape seems to mark the first time he ever played Dark Star or St Stephen, since the band has to show him the chords. (They're unmistakably showing him several parts.) He doesn't seem too comfortable with the electric organ sound, either. Combined with the grueling Eleven rehearsals, it's little wonder he's not dropping in classical-style improvs here. And with a stumbling new guy onboard, it also makes sense why the band is less confident & more painstaking than in the summer live shows.
So I have to give up my theory of the unknown keyboardist! Now that we've agreed it's TC, I think it beyond doubt that this rehearsal predates his joining the band live on 11/23/68. Not only is the Dark Star very underdeveloped for December '68, it begs belief that TC's playing in Dark Star & St Stephen could be so poor after playing them in several live shows on that tour. (Unfortunately he's all but inaudible on the 12/7/68 tape.) So I believe he was visiting the studio while on leave, as he had during the Anthem sessions. No idea where the "11/6/68" date came from, but it may well be true. I think it's in the right general area, anyway. If someone does ask TC about this tape, it may be more fruitful to ask him in general about the early rehearsals & planning for his joining the band - it seems he didn't walk onstage on 11/23/68 totally unrehearsed. According to his "TCBase" he played with the Dead in a September '67 show (in Las Vegas) and on 3/11/68 - shows which arouse the deepest curiosity on my part, but alas we can't hear them. And in the late November '68 shows, apparently Pigpen was still playing organ along with TC (which would have eased the transition), but unfortunately those don't survive either!
