There are, I think, two possible approaches to this recording. One is simply to listen through it and let the effect of the (very different) pieces on it wash over one, reacting to each in turn. The other is to read the excellent booklet notes by James Pritchett and then listen to the music, following in more or less detail what he explains in them. Either process would work, because the music is intrinsically interesting and frequently very impressive.

The opening work is Five (1990), the first in the composer’s series of ‘number pieces’ which, as Pritchett explains, do not specify an ensemble but are suitable for voices: ‘The five parts have particular pitch ranges (mostly on the higher side) and any voices or instruments that can play the pitches can play the piece.’ What the unsuspecting listener will be surprised by is the atmosphere of the piece, suggesting at times both the micropolyphonic density of Ligeti’s Lux aeterna and recent, more ‘accessible’ choral pieces such as Whitacre’s Lux aurumque.

Hymns and Variations (1979) is in some ways more radical. It is built upon two hymns by William Billings in which notes are subtracted, others stretched out, to distort the original harmony in very surprising ways – as Pritchett says: ‘Through selective erasure, Cage gave Billings’s music a bit of harmonic amnesia.’ These pieces also, charmingly, expose a certain unexpected fragility in the sound of the Latvian singers, by which I do not mean to imply any technical criticism but simply an unusual window into the nature of the individual voices of the ensemble.

Four² (1990) was written for a high-school choir, and is based on the letters of the name ‘Oregon’. It is both challenging and remarkably simple, with many passages of great beauty and some dramatic changes of texture. Far more radical is the substantial Four⁶ (1992), which not only does not specify an ensemble but leaves the sounds to be produced up to the performers. The harmonic structure itself is what Pritchett describes as ‘anarchic’, arising from the way in which tones overlap, and completely outside any conventional scheme. Here, too, one is unsurprised by the unconventionality but taken aback by the richness and variety of the final musical result. It must be said as well that the singers sound as though they are enjoying themselves enormously.