OK, We may agree on the origin of the curious tradition of wishing "merde" as a blessing for good luck for our fellow artists.
But more than a century has passed and people ar not going to theatres in horse carriages any more. Not even in Paris. (JJK)
So I think we should find a modern expression to wish good luck -without mentioning thos awful words!.
OK, but what? Finding new, apropiate expressions is the goal of this thread. And also that we amuse in the process.
A few ideas come to my mind, but they are not too elegant: e.g.
lots of smog! (too old fashioned, even for London)
lots of CO2! (too technical, not for real artists)
lots of NO! (Nitric Oxide, another pollutant) Sounds too negative and would be only for chemists...
lots of Benzopyrenes! This one sound nice, but may require a master in environmental sciences to understand. We could always explain it here to rationalists but ...
Sorry, I ran out of ideas for the moment. It's your turn now...
I only managed to come up with "Car!" ocr maybe "Cyclist!", the latter more appropiate for a walking musician. But they are not very exiting, and you need to know the merde-background to find it intersting at all.
Today you would probably use SMS, Twitter, maybe a PM on this forum, or anything like that to send a good luck wish... But what to say?