The Kuznetsov NK-12 is a Soviet turboprop engine of the 1950s, designed by the Kuznetsov design bureau. The NK-12 drives two large four-bladed contra-rotating propellers, 5.6 m (18 ft) diameter (NK-12MA), and 6.2 m (20 ft) diameter (NK-12MV). It is the most powerful turboprop engine to enter service. (Wikipedia: Kuznetsov NK-12)
Tupolev TU-95 (NATO codename Bear) and Antonov AN-22 (NATO codename Cock) use the NK-12 turboprop engine, and as can easily be seen in many videos available on the internet, their propellers are not geared in a way that would make them turn in equal rpm.
TU-95 propellers turning ratio is such, that for each full turn of the front propeller, the one behind turns a little more than half a turn: TU-95 engine start on Youtube.
For AN-22 the ratio is one full turn for front prop, and about 3/4 for the rear one: AN-22 engine start on Youtube.
Why such ratios? What is the reason the front propeller has significantly higher rpm compared to the one behind it? The air that has gone through the disk of the first propeller has obviously been accelerated, and has gained a swirl momentum. This would have to be taken into consideration somehow.
My own guess would be that this has to do with the aforementioned flow changes, load distribution between propellers, and/or something with vibrations and resonances of the powertrain.
Please do not hesitate to prove me wrong on this one, but for that to fly, I'd require some hard evidence concerning the NK-12 powertrain.