Norma Winstone faced a decision. Having won a junior scholarship to study piano at Trinity College

in London, she needed a second instrument. A boy she had a crush

on at Dagenham County High

School played the organ, so Winstone chose that.

Unlike the object of her distant admiration, one Dudley Moore, after studying for three years, Winstone found that she hated playing in public. She also found it spooky practising the organ in her local church in the middle of winter. So she gave up and reverted to something she found much more natural: singing. We'll never know what she might have achieved had she conquered her keyboard stage fright and fear of churchly ghosts, and, though she hasn't followed her old school crush into household namedom, the jazz world has been forever grateful that Winstone didn't let her early experiences in wedding bands put her off singing, too.

''The trouble was,'' she says, ''I'd heard Miles Davis by then, and I wanted to do something like that. I was trying to improvise, and people thought I was just messing around with the tune, so I had to stop

doing weddings.''

She had always sung at home. Although shy, she could generally be persuaded as a youngster to sing at family gatherings in the East End of London. And while everybody else belted out Roll Out the Barrel, Winstone, aged eight, would deliver If I Loved You or The Lady is a Tramp.

When the second instrument problem came up in her application to Trinity College, she hadn't considered singing. ''And I'm really glad,'' she says, ''because when teaching, I've met so many people who have been completely messed up by formal training. They've been taught to produce the voice in a way you just don't do when you're using a microphone, as you usually do in jazz, and it just doesn't suit the music.''

Winstone's vocal training came from a saxophonist. ''He taught me about breathing, how to hold long notes and increase volume,'' she says. ''They were exercises that wind instrument players use, I suppose, and I think they worked.''

Others thought so, too, as having answered an advertisement in Melody Maker, Winstone entered the London jazz scene of the 1960s and found her ''singing as an instrument'' in demand. She sang opposite multi-saxophonist Roland Kirk at Ronnie Scott's, joined bandleaders Mike Westbrook and Michael Garrick, briefly ran a jazz club in a venue owned, unknown to her, by the Krays, and got into free improvisation.

As the 1970s progressed, Winstone's name became ever more widely revered among jazz musicians. She recorded with the great pianist Jimmy Rowles, former accompanist to Billie Holiday, and in doing so wrote lyrics for his composition The Peacocks, now much covered as A Timeless Place. ''Words by Norma Winstone'' began to appear increasingly in credits, particularly on compositions by pianist John

Taylor, whom Winstone met in 1966 and later married, and trumpeter Kenny Wheeler, another friend from the 1960s, who joined Taylor and Winstone in the enduring chamber jazz group, Azimuth.

''I'd always been interested in words and I'd hear something that John and Kenny had written, and then all these musicians on ECM Records like Ralph Towner and Egberto Gismonti, and I'd think, why should the instrumentalists get all these great tunes to themselves?''

SHE adds: ''Of course, some music doesn't need words, and once you add them the meaning becomes much more specific, so you have to be careful. But there's a great satisfaction in writing them, especially when someone like Ivan Lins [the Brazilian songwriter who recorded Winstone's lyrics to his song Vieste] sends you a CD unexpectedly, with your words on it.''

Despite working with many of the leading and most interesting names in jazz, Winstone's appearances in Scotland over the years have been rare. Her concert at Glenmorangie Glasgow Jazz Festival this year is her first visit since 1995, and is all the more special for her because it reunites her with John Taylor. The couple divorced some years ago, but remain a strong musical partnership, and there are certainly no tales to rival, say, Richard and Linda

Thompson's on-tour split, when the wronged wife lamped the departing husband mid-song.

''Oh, no, we never got violent,'' says Winstone with a laugh. ''But it wasn't easy. We didn't work together as a duo for a while, although we were both so busy doing other things. The important thing was, though, that the music was there first and that stayed. We just have this rapport. I don't understand it. John's extraordinary. He never bears malice. I love singing with him because he does so many different things, and he'll bring bits of all of them to our gigs. Even if we haven't worked together for some time, it's like a conversation we pick up again. Mind you, and this is a big part of the attraction for me: I never know what's going to happen once we get on stage.''

l Norma Winstone and John Taylor play the Tron Theatre, Glasgow, tomorrow.