From Bill Gallagher:
This blurb from http://www.chicago.8m.com/Champlin/History.html confirms the timeline that Charlie said:
In November of 1970, 'The Sons' got back together, this time without Tim Caine or Jim Myers. They released an album "Follow Your Heart" in April 1971, but they didn't feel that things were working out. Bill Bowen and Al Strong left the group, and were replaced by David Schallock (bass) (from Big Brother and the Holding Co.) and Bill Vitt (drums) (a session musician). With this line-up, the band became 'Yogi Phlegm' from June 1971 to January 1972. That same month, it was back to being 'The Sons', Bill Vitt was replaced by Jim Preston (drums), and added to the group were Michael Andreas (woodwinds), Mark Isham (brass), and Phil Wood (brass). This was the most stable Sons line-up. They released "Welcome To The Dance" 7/73, "Sons Of Champlin" 3/75, and "A Circle Filled With Love" 5/76.
Based on the above, if it was with Vitt (which it was), it was Yogi Phlegm lineup, not Sons II.
BTW, the tape I have is magnetic ca-ca: you could hear it for verification purposes, but you wouldn't want to listen to it. However, there is a clearly audible introduction by Bill Graham of Champlin, Garcia, Lesh and Vitt.
There is also the issue of where the stage was located at Winterland. There were one or more periods of time when the stage was on the right side of Winterland (as you enter from the front). Most of the time, and all the time after maybe ~1973, the stage was at the back (as you enter from the front). I remember this sons-phegm/garcia-lesh jam visually as being on the right side stage alignment. (But I could be wrong...) If anyone knew the date brackets for the stage positionings, this may or may not help.
The only Dead
Winterland shows I went to in 1971 was 12/31. And I recall the stage that
night was in the "back", not on the right. I definitely did not
go to the March or May 71 Winterlands. (Well, I might have been at the March
71 show. If the Sons were there then, then maybe it could have been then -
that) My only problem with dating this show as 12/31/71 is that there were
alot of people there, especially that night, I would think this Champlin-Vitt-Garcia-Lesh
jam would have been noted somewhere already on all the numerous and seemingly
comprehensive dead lists, garcia lists, etc.