Cheesy as it may be, 10cc's "I'm Not In Love" has really amazing production (listen with headphones for the full stereo effect), considering when it was recorded (1975 or so). It would probably be pretty easy with modern samplers and synths. Any, wikipedia comes to the rescue:
A collaborative effort built around a title by Stewart, "I'm Not In Love" is notable for its innovative production, especially its choral backing. This ethereal sound was created by laboriously building up multiple overdubs of the voices of Stewart, Godley and Creme singing a single note in unison. This multitrack was then mixed down and dubbed down onto 16-track tape. This process was repeated across all sixteen tracks to create a lush 256-voice 'virtual' choir that could 'sing' chromatic chords. A number of these prepared multitracks were then cut into several endless loops, each which contained the basic notes of the main chords used in the song. The chorus loops could then be played by using the mixing desk rather like a keyboard -- each chord could be sounded by bringing up the fader for that loop. In this pre-sampler period, the group were able to simulate a large polyphonic choir, creating a dramatic tonal effect similar to that produced by the well-known choir setting on the Mellotron, but with a far richer sound, and in full stereo.