Microtub are a trio of microtonally tuned tuba players. The UK born Berlin resident Robin Hayward is joined here by the Norwegian pair of Martin Taxt and Kristoffer Lo, and the trio perform works based on Hayward's tuning vine, a mathematically developed microtonal system which he developed after attempting to visually depict the various harmonic spaces found inside his tuba. However it came about, the music on Star System's two pieces is quite beautiful. The deep roars of the three carefully tuned instruments purr out long lines of tone that overlay one another, sitting like almost opaque strata above one another until the physicality of human breathing and the gradual shifts in Hayward's composition introduce a sense of flux. The effect is of a delicate yet hefty drone that thickens and thins like massive bellows eased in and out.