IIRC, Richard Carpenter took this to the Nth level. He found the recording equipment with the largest number of tape tracks - 28 - and used them all to layer Karen's voice.

She had an amazing voice, but she also stood out because of his technical nuancing of their sound.

I'm super late with this reply, but they were also the first to close-mic drums. Before that, drums were always recorded with a couple of mics above the kit.