Whether or not he would admit it, playing jazz piano in the cafés of post-war Cologne left its mark on Stockhausen’s music much as the war itself had torn his family apart and scarred him for life. Each listener will find their own way into his world, but the key in the lock for many has been Mantra (MANTRA, in the composer’s own eccentric capitalisation). One factor must be the work’s relatively modest performing demands for two pianos and ring-modulating systems, which effectively ‘prepare’ the instrumental sonorities in what at the time (1970) would have looked like a hi-tech update to John Cage’s nuts and bolts.

The Neos booklet reprints Stockhausen’s familiar floorplan for Mantra, of a 13-note formula, repeated and superimposed over the course of an hour. In the listening, though, I find it more helpful to think of Monk (Thelonious) than monks. The work’s title raises expectations of relationships with chant and chanting which Stockhausen had already explored in Stimmung (1968), and even practical experience with Taizé or Buddhist rituals will hardly prepare the listener for the formula’s free-form turns of phrase and direction.

The GrauSchumacher duo have recorded Mantra before, for Wergo, and headphone listening brings out the more sophisticated synthesis of instrumental and electronic elements on this new version made with the SWR Experimentalstudio (descendants, in effect, of the WDR studio in Cologne where Stockhausen had cut up bits of tape to form his breakthrough work, Gesang der Jünglinge of 1956). A deeper and wider soundstage also enhances the potentially immersive experience of Mantra, so that it more effectively emulates the wrap-around live-orchestral canvas of Gruppen (1957). Despite the (very) gradual accumulation of energy in Mantra towards a theatrical climax, I find even the new version retains an oblique, hermetic austerity which may be germane to the spirit of the title, and so I would still point Stockhausen initiates towards Gruppen and Stimmung first. Taken on its own terms, however, this Mantra redux deserves definitive status.