Ringo at the mixing desk | Fab Forum

I'm looking for a clip I know I've seen but I can't remember from what. It involves Ringo sitting at the mixing desk talking about George Martin and he says something along the lines of "Everything runs through here and then George Martin presses some buttons and he can make the guitar sound like a piano, and you might ask, well why not just use the piano, because the piano sounds like a guitar." 

If anyone can link me to the clip or even remembers what documentary it's off I would be hugely appreciative.