The Invariant might be taken as a neat summation of where the jazz piano trio is at right now – not at the most progressive end of the musical spectrum, perhaps, but not at the most conservative pole either. This is state-of-the-art small-group music made somewhere in the middle. The three players – leader Benedikt Jahnel, double bassist Antonio Miguel and drummer Owen Howard – are from Germany, Spain and Canada, respectively, and together they offer a smartly empathetic American-European distillation of the jazz tradition: coolly intelligent but with an awareness of the need for a little swing and sparkle; reserved but poignant. They've been together for a decade, unchanging in their set-up (hence the album title), and the disc gathers together eight numbers penned by Jahnel across the past half-decade, honed in live performance and otherwise refined. The results are extremely accomplished without ever quite generating the kind of energy that would make The Invariant unmissable.