Kenny Garrett, Ronnie Scott's, London <!-- none onestar twostar threestar fourstar -->

From the moment Kenny Garrett strode on stage, the skull-cap-wearing prophet of the alto sax began roaring through "Chief Blackwater", his tribute to McCoy Tyner, going straight into a 15-minute solo that picked the audience up by the earlobes and seared onto their brains an imprint of what it means to have drawn so deeply on the well of jazz that nothing but its essence escapes from his horn.

It was the most uncompromising yet utterly captivating exposition of post-bop to have issued from the stage of the Frith Street club for a long time. Backed by a rhythm section that fitted as snugly to Garrett's sound as his trademark hat does to his head, the 45-year-old from Detroit twisted thick ropes out of his churning alto, alternating with short wails and extended "off" notes strongly reminiscent of mid-to-late Coltrane. It was severe, but sexy; it swung like hell, but with serious intent.

Then - and this was one of the remarkable aspects of the near-two hour set - the quartet moved seamlessly on to a slowish groove so fat it could have kept a crowd on a dancefloor. Benito Gonzalez switched from grand to Rhodes piano, coaxing tight minor chords from the electric instrument. Garrett himself turned on a distortion pedal that produced such a superior, clear sound that I fancied the late Eddie Harris was nodding his approval from beyond the grave.

The group, driven by the no-nonsense double bass of Kris Funn and insistent drumming of Jamire Williams, continued to touch different stylistic bases, bringing out the profundity and majesty of Garrett's hymn-like "Sing a Song of Songs" and letting the silences speak when he switched to soprano sax for a trio of East Asian ballads.

All, however, was clearly woven from the same cloth. There's occasionally been almost too noticeable a jump between the acerbic swing and the downhome funk in Garrett's repertoire. With this quartet, he has achieved a marvellous coherency. Nothing is employed to show off, nothing extraneous is brought in to lend a commercial edge. Garrett can lock his gaze on to any musical ingredient and command it to serve the purpose of jazz.

I've often thought Garrett is unequalled as the modern master of the alto sax. Now I know it for sure. Jazz is a higher purpose, and a player of Garrett's stature reminds us of that.