However much it runs counter to our youth-obsessed popular culture, most singers get better with age. Baby-faced instrumentalists may dazzle with their energy and audacity, but there's no substitute for seasoned singing. Used skilfully and consistently, the voice slowly settles and strengthens over the years, while all the emotional and psychological attributes that underpin a song's performance - confidence, experience, empathy, imagination - undergo a parallel maturation. CELTIC RADIO: Music, interviews and live shows from Celtic Connections

There can be few more shining exemplars of this than the revered English singer June Tabor, who, 32 years after her debut recording with Maddy Prior of Steeleye Span fame, continues to reap still greater critical praise with each successive album.

"It's obviously not something you're aware of day to day, but because recorded material exists, I can compare now with how I sounded 20 years ago," she says. "I think I have improved, mainly in terms of understanding the needs of songs better. In many ways it's actually about doing less: understanding that the song is the most important thing, not me, and letting the words and melody speak for themselves."

It's a deceptively unassuming approach to her art that has seen Tabor lauded across a diverse spectrum of musical territories. While primarily identified as a folk singer, she's equally renowned as an interpreter of both traditional and contemporary material. Richard Thompson and Elvis Costello have both written songs for her, and she has also worked with jazz and contemporary classical ensembles. The repertoire covered on her recordings has ranged correspondingly far and wide, from mediaeval French love songs to settings of first world war poetry, Robert Burns to Manchester bard Les Barker.

"I suppose I just keep trying to do what I do best, but do it in different ways," says Tabor, who turned 51 on Hogmanay. "The constant is always good songs that tell good stories, but the way they're chosen and arranged and performed subtly changes, often depending on who else you're working with at the time."

After a period of fruitful eclecticism throughout much of the 1990s, her last three albums have largely returned to the traditional material with which she first made her name.

"There's never any plan or agenda," she says of this shift. "It's always about what songs happen along and speak to me strongly enough, either by resurfacing from some long-forgotten corner of my memory, or when I encounter them for the first time. People say all the good traditional songs have been done to death, but it's not true. There's still plenty of wonderful material lurking in old books and collections."

It was traditional song that originally inspired Tabor to find her own voice, an experience she still remembers vividly.

"I was about 15 at the time, and I'd just started going along to the local folk club. My sister knew this was my new passion, so one day when we were out shopping she offered to buy me a record, and I picked out this Anne Briggs EP, Hazards Of Love.

"As soon as I heard it, I was just immediately transfixed. People at the folk club always sang with guitars, lots of Clancy Brothers stuff and so on, but here was this woman singing without accompaniment, making this sound that was complete in itself, just by doing all these amazing things with her voice. I went back to the same shop a few weeks later and bought the Stewarts Of Blair album, and got totally knocked out by Belle Stewart, too. Here was somebody else doing the same thing, but in a completely different way. That was really the starting point for me - including the realisation that this was something you could do on your own."

Fired with adolescent zeal, Tabor wore out her Dansette singing along until she could imitate both Briggs and Stewart to her own satisfaction.

"I have no musical education whatsoever," she says. "I just learned the songs and copied the phrasing by playing those records ad nauseam, trying out both singers' styles. Then I tried putting the two together, and missing a few bits out - and that's approximately what I've been doing ever since. It's also why I don't do singing workshops, because that's about as much as I can tell anyone."

Besides the expressive eloquence of Tabor's phrasing and articulation, her fame rests on the singularly stirring timbre of her voice. Deep, velvety, resonantly shadowed, somehow lush and austere at once, it's an instrument she seems to have been born with.

"It has gone down with age, but it's always been a bit funny," she recalls. "I used to have to switch octaves singing hymns in assembly at school, because everyone else was too high for me. I did have an upper and a lower register in those days, but then the top part disappeared, and the lower end just expanded with use."

Tabor's professional career developed gradually and organically for its first couple of decades before she finally became a full-time musician almost by default. "Until the late 1980s, I always had another job - I was a librarian for a long time, then ran a restaurant in the Lake District for a few years," she explains. "I did my first proper gig in my third year at university, then started singing around clubs and festivals, and after a while - with no conscious effort on my part - I had a second career as a singer."

When the restaurant was sold she decided to turn to music full-time. Throwing all her energy into the one thing was "a revelation", she says.

"Plus I was old enough and awkward enough not to be pushed into anything I didn't want to do. That's meant I've been able to go about things very much in my own way - which may not always be the most financially rewarding route, but enables me to keep on doing what I love, because I keep on loving it."

One direction where Tabor's muse has never led is into writing her own songs, despite the ever-increasing commercial pressures on singers to do so. "I am conscious of that climate, but it doesn't worry me in the slightest," she says. "I do think it's a shame that so much emphasis is put on original songwriting - apart from anything else, there are an awful lot of songs out there that should never have made it out of someone's bedroom. I get ideas about songs that I would like to happen, but I'm not the one to write them - and I know this because I tried writing one once, and it was awful. I also think that the role of the interpreter is often undervalued these days. Having people come at things from the outside, rather than starting off with that intense personal investment in something you've written, is a really important part of songs being tested and judged."

And when Tabor does have ideas for songs, she's in the enviable position of being able to call on the best to realise them. "That has happened a few times. Les Barker and Bill Caddick have both written songs for me based on things I've suggested," she says. "And Richard Thompson's been promising me a song about the intifada for at least 10 years, but I've never seen it yet."

No matter. With one of the classiest back catalogues in the business, June Tabor has plenty gems to draw on.

June Tabor, Strathclyde Suite, Glasgow Royal Concert Hall, January 30 (8pm)