What was Jamerson reading?
 

One of the rare visual records of the great James Jamerson playing is a few precious moments in the excellent Marvin Gaye video (here if you haven't seen it yet).

I'm curious (and I don't know if there's anyway to answer it, other than speculation, but) what kind of chart is Jamerson reading? I can't imagine it being note-for-note standard notation-- who (particularly Marvin Gaye) would presume to tell this man how to play his lines?

Is it more likely a lead sheet with the changes over the words?

Well now, internet synchronicity strikes again. On another thread, on this very day, it is revealed that Jamerson was playing a written-out part. The catch is that the composer used a compilation of Jamerson licks to write the line!

See this thread for the fascinating details.