Having planned a cycle of 21 pieces in six cycles, Stockhausen initially completed only the first 11 over three cycles. Brief and pithy, I IV (1952 53) are preoccupied with opening out a serial technique as conceived by Schoenberg and evolved by Webern before being elaborated by Messiaen. Their musical interest is not exclusively historical but sounds limited next to the broader spectrum embodied by V X (1954 55). This substantial sequence takes in the long-term interaction between sound and silence in VI, the nuanced chordal repetition of IX, then the compendious exploration of pianistic possibilities in X, making this latter a high point of its composer’s output as also of mid-20th century music. Standing in (splendid?) isolation, XI (1956) puts the onus on the pianist to wrest cohesion out of its matrix of spontaneous events.

Interestingly, Sabine Liebner has opted not to render these pieces in their numerical order but as two complementary sequences – each prefaced by a realisation (forwards then backwards) of XI and culminating with the largest two items. Her expansiveness here might surprise those familiar with the pioneering integral recording by Aloys Kontarsky (Sony, 11/68^R), though Liebner’s control over attack and decay in VI is absolute, while her integration of timbral and textural extremes in X unfolds with a formal and expressive inevitability that compels admiration.

The wider influence of these pieces has yet to be fully considered – two instances being that of VI on the compositions of Anthony Braxton and Cecil Taylor, or of XI as a ‘warming-up’ procedure for Claudio Arrau (who apparently agonised over presenting it to his audience). Whether or not at least some of them could yet enter the standard repertoire, their intrinsic qualities as music can no longer be gainsaid – as Liebner eloquently demonstrates. Superbly focused sound and a highly informative booklet note offer further incentives to listening.