For reasons that are not immediately clear, Asmik Grigorian’s Strauss disc comes with the title of “Laws of Solitude”, and as if in explanation the cover design includes a meaningless equation – “4 + 4 = ∞”. But for the soprano, apparently, the Four Last Songs conjure up ideas of solitude, “not an unhappy solitude, rather a journey towards infinity”. In fact her disc contains two recordings of Strauss’s final work; there’s the usual orchestral version, with Mikko Franck conducting the French radio orchestra, and then the songs with piano accompaniments (none of them Strauss’s own arrangements). Grigorian’s rationale for doubling up is that each version of the cycle requires “different colours – even if they are the same piece”.