Led Zeppelin - Houses Of The Holy #3 Over The Hills And Far Away (backward lyrics in red)

In this one they manage to repeat "Hey Lady" at the same time backward at 3:56 and forward at https://www.youtube.com/watch?v=BdLCg7YQMFU&t=52s. It's a very cool effect when you have only the 2 second sound bite and loop and change direction easily with audio software. How they did this with reel-to-reel must have been some tedious work but they had the technology, Ampex is a company that offered reel-to-reel with forward/reverse/variable speed at that time.

https://en.wikipedia.org/wiki/Ampex

How else do you think they did it? Help from above? Help from below? Just pure brilliance?

2:33 Plant also followed a big mouse around, HA!