It’s a bitter pill indeed when a piece you greatly admire is suddenly yanked in a fundamentally different direction by its composer. For me, Terry Riley’s In C was forever a musical allegory for West Coast 1960s liberation. A repeated high C becomes a totem around which a freewheeling body of instrumentalists weave tiny modules of material into a whole that’s structurally loose, but held together by the shared responsibility of assiduous listening. This new recording directed by Paul Hillier is curiously Blairite in its desire to define a “Third Way”; now “a certain amount of vocal scoring” formalises aspects of Riley’s permissive scoring, while the repeating C stops at one point to allow an ideologically dubious climax to emerge.

Authentic performance practice reaching Terry Riley’s music is an alarming prospect and, thank goodness, one that’s not entirely relevant here because this version comes with the composer’s blessing. But, as pieces like Requiem for Adam suggest, there has been a shift towards the mainstream in Riley’s recent work, and it feels disappointing that he’s allowed In C’s radical agenda to be swept along. The democratisation it heralded was powerful precisely because its inherent freedoms obliged performers to be sensitive and alert listeners, and to hang their conservatoire egos at the door.

On a technical level Hillier and Ars Nova’s approach is flawless. Intonation is as clear as a bell, balance is immaculate and the structural proportions are unfailingly symmetric. But is that what In C should really be about?