Jesus Blood Never Failed Me Yet by Gavin Bryars is an extraordinary piece of music. Built around a field recording of an unknown homeless man singing a hymn fragment, it is simple in concept, but deceptively powerful in execution. The fragment loops until it feels elemental, while instruments gradually build and fade behind it. Such beauty lies in the fragility and the impossible optimism in the voice of this poor, anonymous man. Long dead, although we’ll never know for sure what happened to him. Long forgotten, if it weren’t for the existence of this piece. It’s the combination of all that which gets to you.

The story goes that during the making of it, Bryars left the tape running, and when he returned he found his colleagues silently weeping. This performance, by musicians from York St John and to raise money for the homeless, could well leave you the same way.

Before they start, a member of the orchestra advises us not to stay seated, that the best way to experience the piece is by moving to different places round the church. But you may want to find a dark corner so you can lose yourself fully and maybe have a cry. That’s the only shame here – it’s bright, it’s the middle of the day, there are distractions within and outwith the church. It isn’t the ideal circumstances in which to abandon yourself and truly experience it, though it is still incredibly powerful.

The performers are stationed round the church – brass at the front; a small choir to the right; guitar, accordion, glockenspiel and percussion to the back. It’s out of keeping with the piece to comment on their performance – they’re accompaniment, not main feature – only to note that where strings dominate in the principle recorded version, accordion and glock provide a subtly new setting here. In common with the gradual build of the loop, you can’t actually tell when the musicians and singers have started. You slowly become aware there is a new sound in the mix; it’s almost imperceptible at first. Hide out of sight of the speakers and you won’t know where the homeless man’s voice is coming from either. It’s a surround sound experience like no other.

In our atheistic age, religious experience is easily mocked. But our unknown singer felt it, and something similarly transcendental is happening in this church as we listen. You leave cleansed, healed and more human for the experience.