| I don't know whether the "Joe Frazier" solo was improvised or constructed in advance...but if I had to guess, I'd say it was improvised at some time, and then Jeff subsequently transcribed what he'd improvised so that he could play it verbatim as a motific device.
Remember, Gradually Going Tornado was recorded in 1980, when it was technically convoluted & rather time-consuming to fly parts around from one location of the multitrack to the other (unlike today). Would've been far faster for Jeff to simply play the solo a second time for the recap.
But to my ear it definitely has the shape, musical vocabulary, and "statistical density" of a Jeff Berlin extemporaneous solo, which is why I suspect it was originally an off-the-cuff improvisation. It's just that that time of origin may have been well before the "Joe Frazier" recording sessions.
Like I said, I'm just guessing. | 
but the man can play a solo. I belive it was more or less constructed. The source wont answer these questions.
