747 distinctive engine sound
I have very happy childhood memories of watching them in the early 70s at Heathrow, as one by the airlines added them to their fleets.
One thing which did make it very distinctive (apart from the obvious hump) was that gorgeous low pitch engine drone. Can someone please tell me the engines which made that sound? I've tried looking on YouTube for 747 videos but none of them have that sound. I'd love to hear it again...