Jan Garbarek (saxophones), Hilliard Ensemble

Christ Church Cathedral was packed last Friday for the first Dublin appearance by Jan Garbarek and the Hilliard Ensemble. Bringing together a leading jazz saxophonist and an all-male vocal quartet that specialises in early music might have seemed an unlikely recipe for success. But their blend of old and new, with Garbarek improvising around the voices, has proved captivating to listeners on CD and in live performance.

The formula, which initially involved improvisations over pieces from the Hilliards' repertoire, has now been broadened to include rather more freedom for the singers. But the basics remain the same. The singers, whether singing straight, branching out into overtone singing, or engaging in some minimalist looping, inhabit one world, the saxophone another.

This is actually the formula's great strength. Garbarek and the Hilliards are both leaders in their respective fields, and, together, they both do what they do best. But the division of responsibilities is also a limitation.

There's nowhere really for the performances to go.

Garbarek switches between soprano and tenor saxophones. His improvised arabesques at times take on a middle-Eastern hue. He plays rhythmic patterns by key-clicking and foot-tapping. The performers don't spend all the time on the stage, so that spatial effects, with haloed sound emerging from the periphery of the cathedral, are opened up.

But apparent variation is not great. The effect is rather like a certain strand of new-age music. Whenever you switch in, it sounds interesting. But, like an elaborate, non-repeating wallpaper pattern, it never actually goes anywhere. Improvisation may suggest a notion of unpredictability. But that's the one quality that Friday's performances lacked. You could, of course, look at this another way. What Garbarek and the Hilliards offer is a world of perfection. But at a price.