Mellotronists

My understanding from reading an article contemporaneous to the album 
(possibly in Rolling Stone) is that they used the multitrack recorder 
almost as a fader-controlled Mellotron, with many tracks (if memory 
serves, something on the order of 48 tracks just relegated to this) 
each one containing one sustained vocal note, and that during 
production, they just "played the faders" to bring in and fade out 
specific pitches to build the harmonic structure of the song.

I'd sure like either confirmation or supported contradiction on this. 
Listening to it with smarter ears now that I'm older and have been 
doing this for a while seems to confirm the likelihood of my ancient 
recollection, but it would be nice to have that authenticated.