Mellotronists

I'd be interested to know the names of the 8 people singing on the 
choir tapes. (Should they get royalties from all the artists who've 
used their voices?)
 Which brings up another question...maybe Martin knows the answer. 
Since Harry Chamberlin had male and female voices on his machines why 
didn't Mellotronics make any vocal tapes until the M400 8 choir sound? 
You'd think someone might have suggested it for the MK2 or 300.