Bridge began its survey of Arlene Sierra's music two years ago with a disc of ensemble works. The second instalment is devoted to orchestral music, and the four pieces included span more than a decade of the US-born, British-based composer's development, from Aquilo, begun in 1999, to Moler, which was finished in 2012. Together they show a sure-footed progress; though the handling of the orchestra and the plotting of the musical scheme is more quirky and individual in the later pieces than it sometimes is in Aquilo, which is startlingly fresh and assured for a first orchestral work. In the piano concerto Art of War, Sierra's fascination with tactics and game theory emerges again, in a two-movement work in which the piano's hyperactivity eventually overcomes the weight of the orchestra. The starting point for Moler was apparently teeth-grinding, and for Game of Attrition the idea of applying the rules of Darwinian natural selection to the orchestra. But neither piece needs knowledge of that background to make its points, as the ideas are vivid in their own right.