Technically, the Filet of Soul tracks in Dean's possession are Screen Gems masters.
By contract, everything Jan recorded and produced (or wrote) was owned by the company, including alternate takes, outtakes, and unreleased material. All such material is now owned by Universal (previously EMI Capitol).
When I was writing the book, Dean told me that United Artists (the successor to Screen Gems in the early '70s) did not want the tapes back after he compiled "Side Four" for Anthology in '71. Dean said that's why he kept the tapes.
There was a story previously that he got the discarded tapes out of the trash.
As far as I know, there were no such tracks with sound collage-type overdubs at EMI Capitol when I was doing my research. Universal does, however, still have all of the source material from the two concerts recorded at the Hullabaloo nightclub in December 1965, onto which the sound effects were grafted.