It is a little hard to remember the exact years involved, but I believe that we still were allowed to have the piano a little past 1975. I know my mom bought one and donated it to the Yukon, OK congregation when we built that hall - and I thought that was right about 1976 or 1977. Shortly thereafter came a letter from the society to get a record player and use the vinyl records in the interest of "consistency" of worship - whatever that meant. The assembly orchestras disappeared at the same time for the same reason. Pissed off a lot of really dedicated people who worked hard to do that mini-orchestra effort.
We were not ordered to get rid of the piano; it just fell into disuse after the edict.
I once got into serious trouble (and nearly demoted as assistant magazine servent) for ripping off my best shot at "Frankie and Johnny were Lovers" at a meeting in the Oak Glen congregation about 1966 or 1967...seems the guest speaker did not show up on time, and the WT overseer just asked me from the platform to "play something to pass a few minutes" until he could arrive. I thought he actually meant "play something you know" when he really expected a random kingdom song. I was no longer allowed to play the vapid kingdom songs, but they still "let" me pick up the magazines from the post office and stick them in the slots.
My younger sister got my jehovah-hymn playing job.