Terry Riley's In C consists of fifty-three musical 'fragments', which range from single notes, repeated notes and short melodic phrases. Over a pulsating 'C' (though this is optional), performers move from one to the other, the piece terminating when all have reached the final two-note figure.

Riley’s In C has become a 'classic' of both minimalism (probably the first such composition to achieve comparatively wide exposure, not least via a composer-led CBS recording made in 1968) and of 'communal' decision-making as regards performance given that each performer decides when he or she should move onto the next musical segment.

So a carefully sculpted, conductor-led rendering, is arguably contrary to the somewhat amiably anarchic – and democratic – spirit of the original conception. This is what we have on this Ars Nova release, however, and with the composer's approval – according to the booklet notes by Paul Hillier. Riley encouraged Hillier's idea of a primarily vocal realisation and sent "a version of the score in which the notes were underlayed with 'sacred symbols' for the singers to use."

Quite what these 'sacred symbols' are is not quite clear, nor is the singing distinct enough for them to be recognised purely aurally. In any event, this is a beautifully manicured performance, with the singers' entries finely graded – with gentle 'fadings' in and out – and mellifluous percussion sonorities including some especially effective gong strokes.

But is all seems many miles away from the much 'rawer' Riley-led account. There have been other recorded performances, including an 'electro-acoustic' version that I have not heard. Whilst Hillier's account is undeniably beguiling, In C takes on the character more akin to a carefully crafted fully composed work, say by Steve Reich, to whose own Ensemble the combined singers of Ars Nova Copenhagen and the Percurama Percussion Ensemble – wittingly or otherwise – bear a striking resemblance.

There is still the incessant rhythmic drive inherent in the score, but this is offset against the singing which often has a 'legato' quality for phrases which suggest a more 'staccato' articulation. About 8 minutes into track 3, there is an absolutely bewitching moment when the C pulsation ceases and the voices are left unaccompanied creating a most haunting 'still-point' in this otherwise 'busy' piece.

So this is a release which poses some interesting questions, not least with regard to a composer's changing intentions with regard to the authentic performance of his own music, since from the 'rough edges' of Riley's initial conception – and subsequent performances – here is something altogether more 'manufactured' and 'polished'.

Undoubtedly captivating as it is, one cannot help but feel that something of the spirit of the time and context in which In C was conceived has been lost. But the composer approves, and Hillier directs what is, on its own terms, a thoroughly convincing reading, sung amiably, played precisely and with ideal recorded sound.