Jan Garbarek & The Hilliard Ensemble, St George's, Bristol

Some of the most beautiful sounds in the world

That Norwegian jazz saxophonist Garbarek and English vocal quartet the Hilliards are still touring the ecclesiastical venues of Europe seven years after the release of their first, incredibly successful, partnership on the album Officium is perhaps surprising. Is there anything left to say? Well yes there is, and their continuing willingness to work together should be cause for general rejoicing. The music has changed and deepened since the release of a second album, Mnemosyne in 1999, and this performance (the second of two at St George's last Thursday, both sold out), showed a further, quite radical, departure from that repertoire.

The principal change is that the once rather stiff Hilliards now improvise expertly themselves, and as a result the overall effect is much less predictable than before, if no less beautiful. Garbarek still shoots airy, contrapuntal, blasts across the choral bows, but the voices have begun to echo (sometimes quite literally) his free-roaming role, expanding the definitions of vocal music to include elements of speech and noise. At one point, the tenor Rogers Covey-Crump sat at the back of the stage producing didgeridoo-like drones from his throat while beside him counter-tenor David James – whose voice is one of the most beautiful sounds in the world – trilled like a particularly inspired budgie.

The inclusion of more folk-derived material in the repertoire, including a kind of Norwegian hoe-down, with Garbarek clicking out the rhythm with his feet like a clog-dancer, offered further opportunities for the Hilliards to experiment.

In response, Garbarek has become more jazzy and less emotionally restrained. While in the early music pieces he still tends to repeat the same brief phrases again and again – and it's here that the Officium formula, if it can be called that, sounds most over-familiar – there were two inspired solos that served to remind you just how powerful, and how soulful, a saxophonist he is. For the first, Garbarek made his soprano sax capture the gospel-preacher's moan once echoed by alto players "Cannonball" Adderley and Sonny Stitt, while the sing-song pitching recalled Ornette Coleman. In the second, on tenor sax (which he played more than usual but still less than you wanted), he began like Albert Ayler and ended up like Sonny Rollins on Don't Stop the Carnival, rolling out huge blasts of thunderous noise.

The other highlights of what was a truly superb concert were often to do with the venue itself. Since the beginning of their partnership, Garbarek and the Hilliards have exploited the sonic potential of the buildings they perform in, and both the physical and acoustic environment of St George's offered a much more intimate setting than usual.

Deprived of the long echo of a medieval cathedral or abbey, the music had less pomp and more humanity. As the performance was lit partly by candlelight, it looked wonderful too. I could still have settled for 15 minutes less music than we got, but everyone else wanted even more.