After a warm reception last March at the Gateshead Jazz Festival, classically-trained Swiss pianist/composer Nik Bärtsch returned to the Sage earlier this week with his band Ronin to perform a mixture of new material alongside works taken from their most recent album Holon on ECM Records.

The versatile musician, who last month received a commission from world-renowned new music institution Bang on a Can, was in the UK for four dates on a short UK tour which finishes tonight.

Before a note is played, the unusual combination of instruments sitting on stage suggests that an interesting soundworld awaits. As you scan from left to right you wonder what the abnormally large woodwind instrument might be? It is in fact the contrabass clarinet belonging to reedsman Sha, who with incredible stamina uses it to churn out some mean riffs and growls.

Bärtsch certainly has a penchant for the lower registers and he explains to me that this is why bassist Björn Meyer is given plenty of space to improvise. For the others, improvisation becomes an exercise in restraint. Against the busy, polyrhythmic, and funky minimalist soundscapes – less is more. From quiet meditative beginnings, the pieces build in rhythmic and dynamic intensity, often ending with a live fade-out which completes the structural cycle.

In these mesmerising performances Bärtsch leads the way in exploring timbre, scraping the innards of his piano, and playing pulse like figures with muted strings. Percussionist Andi Pupato experiments too, with exotic shakers and other ethereal noise makers providing a nice contrast to the mostly traditional kit of drummer Kaspar Rast.

It is worth pointing out that despite the impressive array of laptops, effects boxes, and futuristic earpieces, the whole performance is created live without backing tracks or the aid of loop pedals. Bärtsch tells me that the computers are used just to ‘clean up’ the sounds, and indeed the overall sound quality is impeccable. After a slick non-stop set the audience is finally given the chance to applaud and the band end on a high with a hard-hitting funk groove as an encore. Whether or not this is jazz isn’t important. Genre-defying Ronin perform powerful and complex music which captures both heart and mind. – David Tshulak

Nik Bärtsch’s Ronin are at the ICA in London tonight. Tickets: www.ica.org.uk