Not that it‘s particularly helpful with the identification, but: „spielen“ wouldn‘t mean „playing“ , as in playing music, in the context Lehndorff is likely using it when reporting on social occasions with the Queen and Frau v. Keith. It means „gambling“. Of which there was a lot going on, at the court of both queens. SD loved gambling even in FW‘s day, when she had a very limited budget to gamble with. At EC‘s court, there were mainly two games - „Quinze“ and „Pharao“. Most of the courtiers preferred Quince, EC prefered Pharao. Lehndorff at some point decides to quit gambling, not least because his colleague, Chamberlain Müller, is really ruining himself several times over. (Thiebault also reports on that, as an example of EC being kind because she didn‘t fire him.)

Quinze later according to German wiki became Blackjack in the US, according to English wiki it‘s 21. Pharao is known as Faro in English. Müller aside, people weren‘t known to ruin themselves at the Prussian court via gambling the way they did at Versailles, but it was a very popular past time, which makes sense if you think about it. Lots of people can participate, you don‘t need to be highly educated or musically talented, and it provides some kicks. For the Prussian court, it became additionally popular during the evacuation times because it was something you could do even when camping out in Spandau or Magdeburg.