Tomaschoff has an artist father and a mother who is an obstetrician-gynaecologist. He vividly creates the backdrop for the identity-busting revelation, which comes after a cosy Vermont cottage family dinner of salmon accompanied by Californian chardonnay. When he informs them that he is planning to take a DNA test with 23andMe, the genetics and research company, his father, who he says sometimes has a temper, lets rip. It is clear all is not well.
The show is sparkily written and pacily performed by Tomaschoff, now 33. In it he melds 13 finely crafted, rhyming songs with a graphic tale charting his journey from a lovingly indulged only child, secure in his unknowingly fabricated identity, to an entirely unexpected new persona. As well as Vermont the journey takes in New York and Toronto and psychologically it traverses a battleground filled with angst, anger and insecurity. This is leavened with arch humour and an overriding sense of positivity about what it is to be a human being.
It is invidious to pick out individual songs, but "Our little secret" has a snappy wit that brings to mind "The Muppets" at their best. The number involves Tomaschoff sticking a red and black sock over each arm as he mimics his parents' cloak-and-dagger conversation with the doctor in the fertility clinic - himself armed with a catalogue of donors. Equally clever is "People will talk", in which he dons a headscarf to impersonate a Yente-like gossip from "Fiddler on the Roof" while lampooning his Jerusalem-born father's fears over the communal reaction to his infertility. And then there's the uplifting, anthemic "Brothers".
The musical, which has minimal props, is slickly produced by Russell Citron. The songs are composed by Ryan Peters, childhood friends of Noam from the Community Hebrew Academy of Toronto Jewish high school.
Our Little Secret: The 23andMe Musical
Gilded Balloon Patter House, Downstairs, until 26 August