Obviously the picture has nothing to do with the music inside, which was dance music for the high society in a city proud of its style. Patched trousers would be a no-no even in more modest dance establishments.

The sign in the center has been bleached, but is still recognizable as containing Hebrew characters. My guess would be a Yiddish-speaking band from rural areas, far from Vienna. One player is using a funnel as a "trumpet".

Sad to see that publishers miss the cultural context, possibly on purpose, for sake of a pitturesque cover.