It may not be enough to assess this show on the merits of William Finn’s music and lyrics. It also seems we must look beyond his and James Lapine’s book — about a Jewish, gay man in 1970s New York who leaves his wife and son for a male lover — and further even than the cast’s performances, all of which are very good.

Because with significantly Jewish shows it now appears it is necessary to take into account the issue, recently raised by some Jewish theatre practitioners, of cultural appropriation. And if you can detect a note of reluctance to allocating space and time to this subject, you may be right.

The complaint by these Jewish theatre makers is that apart from the show’s creators, this work, which started out as a one-act song cycle in 1981 before maturing a decade or so later into a more fully formed work, the UK cast and creative team of this production lack the necessary ingredient to guard against an inauthentic portrayal of Jewish culture. Which is to say, according to the complainants, this show apparently has no Jews. Jewish culture, it is feared, is being appropriated, “erased” even, by gentiles intent on representing Jews, but without including any.

So it is now also necessary to take a view as to whether this production of a show that begins with the audacious song Four Jews Bitching in a Room, feels as Jewish as we can assume its authors intended. I’d say it does. As far as I can see there is nothing inauthentic, for instance, about Daniel Boys’s Marvin, whose belated acceptance of his sexuality ignites the musical’s angst, drives its plot and results in his son refusing to be barmitzvahed.

It thickens when his wife Trina (an excellent Laura Pitt-Pulford) falls for Marvin’s psychiatrist Mendel (a funny Joe Montague) and he for her. So it is clear that the cultural heritage that Finn and Lapine are tapping into here is specifically New York, very Jewish and revels — or rather wallows — in that talent for making a psycho-drama out of a crisis.

The result is a show whose protagonists are each fascinated by the their specialist subject — themselves. Granted, everyone has the right to make their own contentment a priority.

But to make it the subject of 21 songs in a lengthy show’s first act suggests an inflated sense of self-importance. By comparison, the musical Company — score by Lapine’s occasional collaborator Stephen Sondheim —is also about people who are less happy than they want to be. But at its heart is the universal anxiety that goes with committing to a relationship, or deciding not to, whereas the anxieties here are specific to the people who sing about them — a lot.

Thanks to Finn’s lyrically and melodically witty score the show coasts along from one well written song to the next. But while everyone in it emotes to the max about their own circumstances, not much feels as if it matters, until the later-written second act when the outside world pops this bubble of self-indulgence.

It happens when Marvin’s lover Whizzer (normally Oliver Savile who fell ill before this performance and was replaced by an excellent Matthew McKenna with scarily short notice) contracts Aids. The resulting emotional heft is too little too late and not enough to make these characters’ fate feel important.

As for authenticity, director/choreographer Tara Overfield-Wilkinson injects more than a hint of hora into the dance moves, but thankfully the cast avoids over-egging Jewish traits and tropes which, thinking about it, isn’t always the case with Jewish actors.