The long gestation of Road Show – formally Wise Guys, Gold and Bounce (which was also recorded by Nonesuch/PS Classics) – could eventually catch up with the 40-year time span of the show if Sondheim were not finally to let it go, once and for all. That’s a joke, of course, but it hasn’t escaped the great man’s notice that the show itself has become a metaphor for the long and winding road of the Mizner Brothers’ family saga.

It always appealed to Sondheim that these real-life, larger-than-life characters (one more fallible than the other) represented the yin and yang of sibling relationships, not to say the flip sides of that elusive American dream. But rich though it is as a concept, the show in both its incarnations (Bounce made it as far as Washington DC) has never really gelled. Interesting that it has got progressively smaller on its journey to New York where it briefly played at the Public Theatre under the direction of John Doyle. The show may have gotten smaller but its impact hasn’t gotten bigger.

As ever with Sondheim, the play’s the thing (book: John Weidman) with dialogue kind of osmosing into song, most of it redolent of the whistle-stop, snapshot, energy of the narrative. I can’t say I much enjoyed Road Show when I saw it in New York – the raciness of its exposition doesn’t allow for much engagement with the characters until the very final scene. There’s a breathless imperative about it all. Moments of reflection – like the mother’s song “Isn’t he something!” (the stand-out song) – are few and far between. Rather more troubling for me – and this is accentuated when the score is divorced from the show – is the extent to which, musically speaking, it sounds more and more like a self-parody of Sondheim. That’s primarily because there are so many echoes of the score which Sondheim was working on when he began penning this one – that is, Assassins. Papa Mizner’s song “It’s in your hands now” is a dead ringer for John Wilkes Booth’s monologue in the earlier show.

Jonathan Tunick’s piano and wind-band-led orchestrations work well, with a touch of Stravinskian acerbity about them, and there’s a wistfully harmonised number, “The best thing that has ever happened”, which makes magic of a monotone while doffing its hat at Harold Arlen. But despite my overriding disappointment comes that searing last duet between Alexander Gemignani (Addison Mizner) and Michael Cerveris (Wilson Mizner) and fleetingly you are in the hands of a master.

Sondheim has called Road Show the longest out-of-town try-out in Broadway history. Maybe some things are just destined to stay on the road.