You can tell a lot about a band from the cover versions they choose to slip into a live show. A Hawk and a Hacksaw's decision to open with excerpts from Bela Bartok's Romanian Dances is particularly telling. In the years before the first world war, the Hungarian composer travelled in eastern Europe, studying its myriad folk musics and gathering inspiration for his own compositions. A century on, Jeremy Barnes, formerly the drummer with American indie band Neutral Milk Hotel and, bizarrely, a postman in Leicester, has been engaged in much the same project - only he has the benefit of 40 years of psychedelic pop history to throw into the mix.

The music he makes in collaboration with violinist Heather Trost and, at this show, Hungarian cimbalom (hammered dulcimer) player Balazs Ungar, is the stuff of fairytale nightmares. When the cimbalom clatters, accordion chords crash and the violin screeches, it is the sound of panic: you feel like you are hurtling through a gloomy wood, chased by witches and bandits brandishing bloody knives. A gentler melody will emerge, only to be swamped in juddering discord. One song conjures up scenes of a Gypsy wedding party in which the dancefloor is slowly cleared by two grudge-bearing uncles engaged in a foot-stomping face-off. It's surreal, furious and thoroughly invigorating.

At the heart of all this is, not Barnes, but Ungar, an astounding musician whose high-speed cimbalom solo apparently merges four rhythms and eight melodies simultaneously and is accompanied by the distinctive thump of jaws hitting the floor. Ungar at once legitimises Barnes's project and lifts it to new heights. By the end, you feel there's another ghostly sound in the air: that of Bartok in the ether, cheering and dancing a merry jig in celebration.