Every town on Earth has its musical secrets, its own distinct histories and traditions, often relatively unknown even to its own inhabitants. Switzerland’s largest city Zürich is certainly no exception. Lurking behind a non-descript exterior secreted in the city’s District 5/Escher Wyss area is Exil, the club established and owned by Nik Bärtsch, the renowned improvisational jazz composer and pianist that proudly calls Zürich his home. Exil is intimate and inviting, a main room with a capacity that reaches several hundred but that with a closeness of scale to feel personal no matter how busy it gets.

There is a sense of community that emanates from its walls, friendly exchanges and greetings pouring forth as regulars arrive and mingle freely with first-time visitors. For tonight is a Monday night, the night every week in which Bärtsch plays a show with his band Ronin, a now-legendary ongoing residency that tonight reaches its 710th instalment. Yes, Bärtsch has played Exil for 710 consecutive Monday nights, save for a few here or there when he was playing somewhere else in the world, and another band filled in. It is an extraordinary run that cannot grow old or stale because of the nature of Bärtsch’s creativity.

For twenty years he has been mining the outer reaches of contemporary jazz and neo-classical forms, elegantly incorporating strands of funk, rock and electronic music, resulting in what has been variously described as ‘ritual groove’ or ‘zen funk’. No phrase comes close in truth, but any description should rely on the importance of collective movement and the combined energies of the musicians in his bands, whether that be Ronin or his other key project Mobile. It is certainly paramount in his most recent record, Ronin’s Awase, as evidenced by its very title, a term from martial arts that specifically refers to the synchronicity of fluid motion between different actors.

Bärtsch, effortlessly modest and composed in person, is very much a founding father of the contemporary Zürich music scene. Aside from his own recordings and his running of Exil, he has established multiple annual festivals in his hometown, including Apples & Olives, the city’s first “indie classical” festival. He is the sort of approachable figure that everybody who is anybody in the region seems to know. Just speaking to him tonight, he has to break off from our conversation to greet countless people as they arrive, all of whom feel some connection to this lynchpin of the community.

Once Exil has filled tonight, both with friends of Bärtsch and the extended scene as well as with many outsiders that news of this most impressive of residencies has reached, it is soon time for Ronin to take the stage. Currently a quartet, they comprise Bärtsch on piano, Sha on bass clarinet and alto sax, Thomy Jordi on bass and Kaspar Rast on drums. One does not make it into Bärtsch’s bands by accident, and these three collaborators are of the highest calibre.

Rast is at times a master of restraint. A thunderous powerhouse of a percussionist, he demonstrates the discipline to explore every gear change that leads up to the full throttle, recognising the importance of the build as much as of the blowoff. When he hits full stride, though, it is like he has the power to dictate tomorrow’s weather. Jordi often stands in repose, eyes shut, resplendent in the same knowledge that underpins every bassist’s psychology: that nothing makes any sense without them. Reedsman Sha is the budding virtuoso of the group. At one stage early on, his bass clarinet appears to become a tracheal extension, whereupon Sha appears to begin beatboxing through it, before bursting into an incendiary improvised solo. Bärtsch helms proceedings from the side of stage, caressing the keys early on, angrily jamming them later on as if trying to keep a wild animal trapped under there.

The new record dominates proceedings tonight, which is split into two distinctly different halves. The first begins in a contemplative mood, Bärtsch conducting his band with barely as much as an occasional glance. An enamel grin blooms onto his face when the quartet lock into the groove that hits just the spot, which is not infrequently. Sha is able to switch tempo and tone on a pinhead and all four musicians combine for a funk-indebted raging 4/4 half-time climax with ‘Modul 36’, Rast drilling into his deep energy reserves to provide the first true fireworks. Lighting is central to the show tonight too, with Daniel Eaton at the helm, accentuating the tight, radical pivots that the band rely on to keep the performance so richly dynamic.

The centrepiece of the show’s second half is Sha’s own composition ‘A’, a maudlin circular sax piece that find its wisdom in repetition. The sense of control is king, a zen philosophical ritual-based track that is in one sense the most sombre of the night, and yet the joy radiates from the players like at no other moment. Bärtsch comments after leaving the stage that the crowd is even stronger than usual tonight and in this moment in particular it shows. The rest of the second half comes from the 2008 album Holon, concluding with ‘Modul 45’, one final explosion of tight, sharp, primal energy, the static build-up bursting into kaleidoscopic ecstasy. A final blast of blinding light and the curtain falls.

The most enduring thought of the night is that this is no one-off. This joyous experience is on offer every single week at Zürich’s Exil. There will be a handful of Mondays this autumn that Ronin will have to miss, due to their pending European tour, but Exil’s loss is a gain for many others. The awase between Bärtsch and his colleagues has been in development for long enough now that they appear to be in perpetual, amorphous, unpredictable motion. The legacy of such long-term regular performances is readily seen in the comfort and tightness between these musicians. But the legacy for the Zürich music scene is greater still.