You wouldn’t necessarily expect to find a world-class free jazz and improv club right in the centre of Geneva, just a few minutes’ walk from the main railway station. But that’s what you get with L’Association pour l’encouragement de la musique improvisée, Geneva’s leading venue for this kind of music. If Cave 12 is Geneva’s equivalent of the Rhiz in Vienna, then AMR is Geneva’s Blue Tomato, with a programme of regular concerts by local musicians spiced up with occasional visits from big hitters such as Evan Parker, Mats Gustafsson and Ken Vandermark. I saw both the Schlippenbach Trio and Gustafsson’s Fire! Orchestra there in recent months, but never got around to reviewing them. Maybe I will one day, although I wouldn’t hold your breath.

Anyway, it was a pleasure to visit AMR for the second of two evenings led by the Anglo-Swiss drummer Nicolas Field. Field’s was a name new to me, but he’s worked with musicians of the calibre of Keiji Haino, Akira Sakata and “Sir” Richard Bishop, as well as being active in sound art and composing music for the Burgtheater in Vienna. On the occasion of this AMR residency he put together a six-piece group consisting of Swiss and international musicians, and called it the N-Ensemble.

The evening consisted of two set-long pieces, the latter of which Field introduced as “From Sand to Dust”. With just a few written guidance notes in evidence, Field allowed the players plenty of room to improvise within the overall structure of the piece. Duo and trio sections opened out into full-group improvisations, with the soundworld characterized by shifting zones of tension and release, punctuated by frequent bursts of turbulence. Key to the latter was guitarist and bassist Jasper Stadhouders, whose stormy riffing provided the evening with its most deliriously out-there moments. I’d seen Stadhouders a couple of times in Vienna playing bass in Ken Vandermark’s Made To Break, but those outings hadn’t really prepared me for the ferocity with which he applied himself to the electric guitar and the flinty resonance of his acoustic playing.

In the best tradition of group improvisation, each of the various members made important contributions to the overall pace and shape of the music. Valerio Tricoli had a fascinating set-up consisting of a vintage Revox tape recorder with no reels, just a single length of tape looped around a mic stand and travelling endlessly through the tape heads. Presumably Tricoli was recording the sounds in the room and processing them in real time via his mixing console next to the Revox. Whatever the truth of the matter, his interventions added a ghostly patina that hovered over Thomas Florin’s ominous piano and Bjørnar Habbestad’s piercing flute. Playing off brilliantly against Habbestad, Anne Gillot doubled on bass clarinet and something called a Paetzold contrabass recorder. This ungainly contraption looked like something a blind person would bring home from woodwork class, but sounded incredible, with Gillot’s fierce, truculent voicings splintering into the spaces left by the other musicians. Field himself was a constantly creative presence behind the drums, his restless stickwork anchoring the disparate elements of the ensemble.

So engrossed was I in the music’s enveloping sonorities that I was surprised, when I looked around at the end, to discover that I was one of only five people in the audience, there having been at least 20 at the beginning. This is probably the only concert I’ve ever attended where the people onstage outnumbered those in the audience, although this is no reflection on the quality of the music, which was never less than compelling.