Alex Horne: Monsieur Butterfly, Soho Theatre

There are many forms of comedy – stand-up, sketch and improv among them – and now Alex Horne has introduced a new genre as he constructs his set during the hour he spends on stage. It's a kind of Heath Robinson or Rube Goldberg device (that is, a machine that performs a simple task in an unnecessarily complicated way), and the anticipation builds as we see it coming together, and finally learn its purpose.

This show was a huge critical and audience hit at last year's Edinburgh Fringe, and the audience are Horne's willing helpers by peeling potatoes, helping him display his archery skills, capturing wildlife and all sorts, as the construction work – involving things such as ladders, plungers, traffic cones and a hotchpotch of material from Horne's home, such as a desk fan, a hamster wheel and miniature figurines.

Horne says he has always enjoyed the construction more than the finished product – thereby neatly covering himself if the completed object doesn't work every night – and it doesn't take Freud to work out that this bit of on-stage DIY is a metaphor for life, Horne's and our own, as he weaves witty tales about dratted squirrels, friendship and fatherhood.

When the moment to test the contraption comes, we are holding our breath, willing it to work

The last is the show's binding theme; Horne talks about being in awe of his father as a child and how the joker gene appears to have passed down to one of his young sons. A point subtly made is that our lives, rather like the machine being constructed before us, balance precariously between two outcomes at all times. The show's title, by the way, is inspired by the scientific phenomenon known as the butterfly effect, in which a small change in one state can eventually result in a much larger event in another.

He throws in some neatly crafted jokes – “My life is spent avoiding conflict... I rarely go to Syria” – odd facts and neat visual jokes as we watch Horne attach this, tighten that and balance something else, and when the moment to test the contraption comes, we are holding our breath, willing it to work.

There are times when Horne himself questions whether this show is actually comedy – he used to tell jokes for a living, he says wryly – and, yes, there is the odd dip as he concentrates on slotting/knocking/fitting something, but he needn't worry. He's playful and effortlessly funny, and the machine – which did indeed function properly on the night I saw the show – is a thing of daft beauty. 

• Alex Horne: Monsieur Butterfly at Soho Theatre until 16 May