I can add something else that might be interesting, relevant to the discussion about his approach to the orchestra, the LSO sessions and all that.
Peter Otto worked for Faicwafln (Famous Asshole Italian Composer With A Five Letter Name) for a number of years, and during that time Faicwafln was asked by Ricordi to look at Zappa's scores and advise them as to whether they should publish them. According to Peter, Faicwafln looked them over and advised Ricordi not to publish them because Frank is such a poor orchestrator. I wondered about a lot of his orchestration myself, when I worked on those pieces. As I said, I don't do orchestral music myself, but I certainly could tell that the chances of hearing the harp or bass flute were remote at best when the brass were doing certain things. Later it occurred to me that Frank was ALWAYS thinking in terms of recording. None of his orchestrational weirdnesses are problems when you close-mike and mix everything. Here's the bass flute UP YOUR ASS, FAICWAFLN!
Along that line, I was interested to hear from David that even those strange orchestrational decisions seemed to work when David heard them live, too, not just on the recordings