As a rule when I listen to new Bartók quartet CDs I pass on the option of following the music with a score until a second hearing, but not on this occasion. A few seconds into the first movement of this extraordinary version of the Fifth Quartet I was already double-checking whether the dynamics were being played as written. Many weren’t. The Zehetmairs career around the notes like bikers on a zig-zag course, tracing arches at speed with what sounds like the least effort. At the fervid build-up at 2'40" they lunge at the music fortissimo though for the starkly syncopated passage a few seconds later their legato handling of the viola/cello lines tends to soften the argument’s impact. It’ll take some getting used to, but I recommend you persevere. There’s savagery, too – for example at 3'40" where Bartók asks the leader to play ff stridente and Zehetmair all but saws through his fiddle.

Don’t expect either a comfortable or a familiar ride. The two symmetrically placed slow movements embrace vivid, often rough-hewn textures, from a quiet chalky treble to fierce full chords. Perhaps the most satisfying movements are the Scherzo alla bulgarese and the finale: both suggest an element of rustic dance, the finale’s quieter music sounding eerily effective, especially at speed.

Hindemith’s somewhat drier Fourth Quartet (1921) predates Bartók’s Fifth by some 13 years. Like the Bartók it is cast in five rather than the usual four movements, the first opening to a slow, shadowy fugato which soon flares to near-rage. Both here and in the ferocious Scherzo the Zehetmair Quartet capture the music’s radical spirit, much as they do for the equivocal, gently marching slow movement.

This is a fascinating CD. With the Zehetmairs you’re rarely aware of bar-lines, more a constant flow of ideas, a compelling journey with a stated destination but with little need of pedantic signposting en route. You sense that the written notes have been fully absorbed and that the playing has become, in a sense, pure instinct.