Writer-director and co-star Mike Birbiglia’s bittersweet comedy drama makes an excellent stab at pinning down the spirit of improvisational comedy.

His film’s tight-knit six-strong ensemble, the Commune, is a struggling New York improv troupe sent into a crisis when one of its members, Keegan-Michael Key’s ambitious Jack, wins a spot on a hit TV show (Saturday Night Live in all but name).

As long-submerged rivalries and jealousies begin to surface, the other members of the group – including Jack’s girlfriend Samantha (Gillian Jacobs) – are forced to take stock of their lives.

As this suggests, there’s a streak of melancholy running through Birbiglia’s movie, but it’s also very funny in places. And when the gang is sparking off one another on stage, we do get a sense of the seat-of-the-pants nature of their craft. As Samantha puts it, we’re watching people put the plane together when they are already in the sky.