The discomfort of strangers: Tender as the night - Phil Johnson on the sweet sound of Jimmy Scott at the Purcell Room

In Tennessee Williams's Camino Real, a character wishes that the mountain violets could break through the rocks that enclose them, and - in the heavy Lawrentian symbolism of the play - tenderness escape the brutalism of the daily grind. The vocalist Jimmy Scott is like one of those violets, his art the tenderest thing imaginable. Like Lester Young, who liked only the softest of textures for his clothing, Scott has chosen a style that is just about as sensitive as jazz can get.

His repertoire of mainly slow ballads is already limpid, but Scott blunts the edges off a tune by slowing the tempo still further and approaching the notes by stealth, jabbing at the meaning of the lyric by weighing each syllable in his mouth before, almost reluctantly, pushing it out to fend for itself. Not that he's a delicate flower all the time; when he chooses to, his big voice explodes in a fog-horn blare, the vibrato quivering as if he kept a remote-control tremolo-arm in his pocket. And as he sings, his arms strike out in an emotional tic-tac, dramatising the lovelorn words by continually exposing the heart on his sleeve.

As if to show that mountain violets still don't have it easy, though, Scott brought the rocks with him in the shape of his band. Less greyhounds straining at the leash than rottweillers homing in for a kill, the piano, bass and drums trio played supper-club jazz at hard-bop pace and volume, forcing Scott to strain for the presence his stature deserves. Since I saw them a year ago, the band has gained a new pianist, a set of tuxedos, and a name - the Jazz Expressions - and one or the other has resulted in delusions of grandeur, for they play both too loudly and too much. As if in compensation for the slower than slow tempos that will be required once the singer joins them, they spend their opening two numbers racing around the chords hell for leather, bassist and drummer getting in as many glissandos and off-beat accents as they possibly can. When Scott emerges from the black back-curtain, the band are already hurtling towards the bridge of 'All the Way' - normally a ballad - and at first he seems way off balance, his pitch as awry as the angle of his dickie-bow tie.

When he settles down on the following 'Someone to Watch over Me', taken dead slow, the magic begins to work but it's a while before he really gets into his stride. After an ill-judged break to let the band chase each other's tails again, he comes back and delivers the highlight of the set, an almost unaccompanied version of 'Unchained Melody' where his voice rings out as clear and true as that of a choirboy.

He follows it with one of his old signature tunes, the impossibly romantic 'When Did You Leave Heaven', a plea to an angel, and sung like one too. By now the audience is enraptured and the tears are beginning to fall. A final reprise of 'All the Way' comes as slowly as it should, and then, amid bows, bouquets and a standing ovation, Scott is back behind the curtain again.

It was, after the initial doubts, a staggering performance. Beyond the camp and the Blanche du Bois mannerisms, Scott appears to reveal his very soul as he sings. The violets may make it through the rocks yet.

(Photograph omitted)