Listening to Per Nørgård’s Libra, you wonder how a composer could write music that at once sounds so invitingly familiar and utterly mysterious. Libra basks in diatonicism; the genteel opening guitar solo could, if you stumbled in unawares, be momentarily mistaken for the backdrop strum of a Simon and Garfunkel track. And yet Nørgård’s harmonic patterns have clearly been filtered through some higher intelligence. Dacapo’s excellent booklet-notes explain how fractal geometry reconnected their man with tonality. But even with that information at hand, Libra remains a thing of wonder.

Nørgård’s description ‘love music for tenor solo, guitar, two choirs and two vibraphones’ is apt. Modelled around the idea of a cantata and written in 1973, texts by Rudolf Steiner and from the Psalms of David are woven around a 10-movement structure that tenaciously renews its expressive juices. Stories overlap stories. Guitarist Stefan Östersjö takes Nørgård at his word as he bends his phrasing to accommodate alien chromatic smudges designed to inject the prevailing tonal pathway with awareness of other harmonic route maps: poco rubato given structural sting. When the choir enter with the first, unambiguously tonal psalm setting, Nørgård creates an inner tension between materials that powers the music onwards.

In the studio, Nørgård arranged his musicians with a view to keeping the vibraphones looking in from the ethereal margins; Libra is all about shifting perspectives on that elusive overlap between an inside and outside world, between plain-speaking harmony and harmony with its own work-it-out-for-yourself internal function. Presumably a successful performance is one that makes this dual harmonic function explicit; and between the Danish National Vocal Ensemble’s immaculate enunciation and Fredrik Malmberg’s sensitive decrypting of Nørgård’s multiple meanings, his composition is revealed as being bold, beautiful and wise. Two a cappella works sign off, orbiting Libra’s universe like satellites of the mothership.