Scottish Guitar Quartet, The Bull's Head, Barnes, London

A quartet in jazz usually consists of rhythm section and horn, most commonly piano, bass, drums and sax. A guitar may substitute for piano, or be used instead of drums to provide a foil for another chordal instrument - one thinks of some versions of Oscar Peterson's trio - but it's arguable that it has not occupied as elevated a seat as the piano in the great ranking of instruments.

Somewhere between the chop-chop-chop of trad and the meanderings of commercial fusion lies an honourable tradition for the jazz guitar, although if I had to choose between throwing Metheny, Scofield and McLaughlin out of the balloon or just Herbie Hancock, the latter would be safe, despite "Rockit". The keyboard just seems that much more satisfying.

This prejudice (for, I freely admit, that is what it is) is triumphantly overcome by the Scottish Guitar Quartet, a semi-acoustic group that turns whatever limitations this combination may seem to have into advantages.

For Nigel Clark, Kevin MacKenzie, Ged Brockie and Malcolm MacFarlane there can be no slacking on the rehearsal front - I can't imagine anyone deputising for anyone in this band - as the group's success lies in the tightness of arrangements which keep four instruments occupying the same range from crossing lanes, winging each other and ending in a pile-up.

Here is an example of the traffic control: two guitars set a pulse going, on which the others play the melody in octaves; dropping down to one on rhythm, another solos; halfway through the solo, a third adds a riff to the support; a fourth weaves a further line, till the quartet merge on a bridging section and it's time for someone else to solo.

It all moves with the smoothness of stage-sets being wheeled on, backdrops being added and subtracted while soliloquists or Greek choruses step into the limelight. Or, to take an airborne analogy: a flock of birds, individuals that mass as one but sometimes let loose outriders to foray before returning to the formation.

It is quite mesmerising, and totally unlike any more conventional line-up, and the relative unity of sound allows an enormous variety of composition. Whatever terrain this quartet traverses, from bebop to classical Brazilian, fast funk rock to Firth of Forth, it is still recognisably the same beast, whereas a piano-based trio donning a similar array of clothes would likely find its trousers at half mast or its flies undone during such a journey.

A small venue doesn't quite do this quartet justice. I would like to hear them in a place where their fresh, clean sound could echo, off cavernous walls or around the nave of a cathedral. If the quartet were to play in the latter, even the most hardened of atheists would find a trip to church had its compensations. They may not want to go every Sunday - this is a concentrated pleasure, and best taken in small doses - but certainly often enough to be recognised by the parson.