That's nothing. I did a similar experiment with JWs.
When I had a car full of JWs, I usually played no music. For a change, I started playing "Flashback Greats from the 60s" and everyone in the car group was happy, and they placed a lot of magazines, and we were able to get an extra territory in due to how quickly we finished the others.
A month later, I started playing Kingdom Melodies. The car group didn't seem to be very happy, nobody was placing anything, they were walking slower between houses, and people were going for refills on our coffee break! We were less productive than when I played nothing in the car.
I couldn't finish my experiment either. Over the next month, our service group started to dwindle down to where there was just me and sister faithful who was almost deaf.