I came across this lost gem today during my travels, "Improvising Rock Guitar Vol. 1", which was first published in 1973 and then reissued in 1981.
It features Pat Thrall on guitar and members from his original San Francisco based band, "Cookin' Mama" accompanying him; Tom Thompson (Bass), Jesse Harms (keys) and his brother, Preston Thrall (drums). As you know, Jesse Harms, joined Pat and Glenn for some of their live Hughes/Thrall gigs in 1982.
Of the 3 tracks included, there are 2 featuring Pat and the band, "Homage To Hendrix" and "Shaker".
Pat Thrall also recently made this available via his Facebook profile
Improvising Rock Guitar Vol 1. Here is a link to files of the book & audio for those of you who have lost your version...