If you ever get a chance to see the play, do post your reaction here
I love movies or plays about famous classical composers, so I hope the show you mention does come to a place near me sometime.
I found the "menage a trois" second act a little disturbing
I used to think that people back then were very prim and proper, but I don't totally think that way anymore. Especially when it comes to Europeans. I may get blasted for this, but I think Europeans are much more promiscuous than Americans are. Maybe it was like that back in the 19th century too...
I would not say "European". The French and the English attitute to these things were quite different, almost the way you see "American" and "European".
I very much doubt this story. Brahms was not one to be interested in normal women, having only seen the "pros" in younger days when he way playing in seedy joints to earn a penny or two. Witness the fact he never married. Not to be overlooked the modern tendency to drag anyone important in the mud, as if to say, "I am worthless, so is must everybody else be and if they are not, I will make them be".