Same here. I recall something about a pressurized cavern in which people would strap on mechanical wings and fly around in 1/6 gravity.

Which one saves more gas:
a) replace a 10 mpg car with a 20 mpg car.
b) replace a 33 mpg car with a 50 mpg car.

From the way the question is posed it is impossible to say. How many miles-per-year does each drive?

Any jazz organist does this when he carries the bass line for the group. There appears to be a complete separation between the left hand which is carrying the bass and the right which is comping and soloing.