Little of Pierluigi Billone’s music has found its way onto CD, but what has (including a previous monograph disc for Stradivarius) is fascinating. Though working nearly exclusively within the domain of unpitched sounds, Billone (b1960) uncompromisingly renounces non-acoustic means. 1+1=1 (the title refers to an observation in Tarkowski’s Nostalgia, that a drop added to another is not two drops, but a larger drop) was written for these interpreters. If the prospect of a 70-minute bass clarinet duo sounds daunting, the music’s slow pacing and predominantly pianissimo dynamic makes for an inward, involving exploration into the nature of the instrument itself. That the instrument is “doubled up” leads to subtle or stark antiphonal exchanges (although the baggage associated with that term is mostly absent) of almost elephantine eloquence. Throughout the piece, but increasingly towards the end, the performers’ voices are also mobilised, and the difference between their (male and female) registers assumes a special significance, given the otherwise rigid equation between the two. Unlike his teacher, Lachenmann, Billone seeks to evoke a ritualistic musical environment (hence his interest in lost civilisations), but there is little or no hint of the nostalgia that such a programme might conjure up (Scelsi?); he prefers to liken himself to an archaeologist. The booklet-notes offer little way into a work that would anyway be difficult to summarise. A term like “cutting edge” has largely lost its pertinence nowadays, let alone its magic; but those who remain curious as to what meaning it might still retain will rate this as essential listening. The performance is exemplary in its commitment.