My Earliest Braxton Memory

I believe the first time I heard Anthony Braxton was while listening to Willis Conover's Voice of America broadcast one morning before school, around '73 or '74. I had heard of Braxton, but I think this was before New York Fall 1974 came out, which was my formal introduction to his music.

The broadcast was a tape from the Newport Jazz Festival, one of those all-star jams where they play a theme, a seemingly endless parade of soloists follow, and then the theme is restated. Braxton just cut through like a knife with his uniquely angular phrasing, and he got the biggest ovation from the crowd. 

Does anyone know the specifics of this performance? I don't think it's ever been released.