Zaum are a magic band. Literally. They do that magic thing called free improvisation in which nothing is prepared or composed; they make the music up as they go along. I’m the first to admit that some free improv is like a bunch of baboons on speed let loose in an instrument shop but these guys sound like the most movingly original thing you’ve seen in a month of Sundays.

After their first two improvisations at their fringe gig on Thursday we knew we were in for an interesting evening. And then something miraculous happened – their spontaneous witches’ brew became suffused with the colours of emotion. The spell had been cast.

Particular moments exemplified this. One was when an improvisation seemed about to end, only for it to be taken on by electric violinist Cathy Stevens playing a spine-tinglingly beautiful but sad melody interwoven with samples of someone speaking softly conjured from the extensive sound palette of electronics wizz Adrian Newton. Another was a wild duologue-cum-joust between saxophonist Geoff Hearn and clarinettist Kate Wimhurst that swung between the consonant and the dissonant and back. Zaum were like storytellers, like actors in a play that touched drama, comedy and tragedy.

They reminded me just a bit of the free improvisations of the great American jazz pioneers Oregon, but their canvas was broader. As I said, magic.