Gillian Welch, Shepherd's Bush Empire, London

Get yer Mojos out for the lass (and her lad...)

Amid the incessant clamour to create labels to slot men into, one crucial social stereotype has been overlooked time and time again. He is not New Man, Old Lad, New Lad or Metrosexual. No. He is Mojo Man, and verily yea shall meet him aplenty at gigs such as these.

For reasons worthy of a book by Nick Hornby, Mojo Men (that's Mojo the serious music magazine, not mojo of the "Yeah, Baby!" Austin Powers variety) love artists such as Gillian Welch. How they delight in pointing out that, actually, that's Gillian with a hard "G" as in "great", not the "J"-sounding gentle "G" of, well, "gentle". How they love the banter that takes place between Welch and her "musical partner" David Rawlings. How they live to breathe in the sweet country purity of this extraordinary artist's music.

What Mojo Men have in common is their ability to deeply understand music that is, on the surface, simple. They can write books on Bob Dylan. (And many do.) They are happy to read 10,000 word articles on why a particular collection of songs is seminal. Welch's genius, meanwhile (in spite of the fact that she is one of those rare women who could probably out Mojo any of them), works in the opposite direction.

Take tonight's show opener, "Miss Ohio", from her latest album Soul Journey. If there were a competition to write a short story in under 25 words, this song's chorus would win it: "Me-o-My-o/ Look at Miss Ohio/ She's running around with the ragtop down/ She says, 'I wanna do right, but not right now'". Feature films have been made on flimsier premises. Raymond Carver eat your heart out.

And how we (for, reluctant as I am to admit it, there's more that a dash of the Mojo Man in me) watch transfixed. How we can't take our eyes from the gangly woman in the floral skirt and cowboy boots whose leg can't help twitching out the rhythm of her songs. How we chuckle knowingly when, after just two numbers, she asks the photographers upfront to stop taking pictures on account of the fact that, "We play pretty quietly. I can hear your cameras from up here and, anyway, I guarantee that whatever pictures you take from now on, I'll be doing exactly the same thing." And then she straps on a banjo in place of her guitar. Hardly the photo-op of the year, but surely worthy of a snap or two.

But this is Welch's world and she has created it and we are just lucky to be momentarily sharing it. And it is a creation; to some degree, an artifice. For while we stare at this country girl playing Appalachian bluegrass that would grace any porch in North Carolina, it's probably worth reminding ourselves that, in fact, Welch was born in California. The offspring of a one-night stand between a musician and a 17-year-old Columbia freshman, she was adopted by Ken and Mitzi Welch, a husband-wife team who wrote themes for films and TV. She then went on to study at the staid and legendary Berklee College of Music in Boston, where she ran into Rawlings and fell in love with bluegrass.

It is this background that has made Welch the artist she is. All she knows is that dad was a musician passing through New York in 1967; "He could have been Keith Richards, he could have been Bill Monroe," she has said. Certainly, Welch borrows from both. While her music is pure and sweet and fresh as the mountain air, her lyrics reveal hippie leanings, bohemianism and much urban sophistication.

Tonight, Welch rips through every song you could wish for - she even plays "I'll Fly Away", from the O Brother, Where Art Thou? soundtrack, so perfectly you don't even miss Alison Krauss. This is largely thanks to her unbelievable partner. With his new pink shirt ("A souvenir from Jermyn Street"), Rawlings grows in stature each time you see Welch. And while country music is littered with male singers coaxing shy girls out of their living rooms and on to the stage, in a reversal of the traditional gender relationships, Welch has performed the same miracle on Rawlings. Where once he just added whispered harmonies and played the fancy guitar parts (imagine James Burton and Django Reinhardt rolled into one), nowadays, they share the stage in every sense and his vocals (which, tellingly, are the female parts) soar and complete the picture.

So we get the heartbreaking and autobiographical - a rarity for Welch - "I Had A Real Good Mother and Father". We get a cover of Hendrix's "Manic Depression", and we get old favourites such as "My First Lover" and "Caleb Mayer".

In short, we see that increasingly rare sight: musicians so perfectly practised and in tune with each other that they make what they do look simple, like you or I could do it. We couldn't. Which is why we are fated to forever roam the world as Mojo Men.