To get an idea of how Bill Frisell sounds on guitar, listen to his speech. It is full of abrupt stops and starts, protracted slurs, thoughtful silences and the occasional sentence that despite its sincerity doesn't quite make sense.

What his speech fails to convey is his intensity as a composer; his unique ability to capture both reverence and terror in just 12 bars of music. Fans of contemporary jazz have long admired this Denver guitarist and their enthusiasm is spreading to listeners of rock and country & western, an audience generally suspicious of jazz music.

In fact, rock fiends can't get enough of Frisell, and there should be as many shaggy perms as goatee beards among the crowd at London's Barbican this Saturday where Frisell is joined by other top American improvisers.

It makes perfect sense to include Bill Frisell as part of the Barbican's Inventing America season. He is a modern musician who possesses a vast vocabulary of sounds from virtually every genre of music to have originated from the States.

Gone, Just Like A Train (Nonesuch Records) is Frisell's 20th album and possibly his finest so far. His yawning, twangy legato notes and the slurred bluesy horns evoke fairground America while the dark, amorphous abstractions bring to mind a tormented urbanity.

A relentlessly eclectic approach has left some observers wondering whether jazz is a redundant word to describe Frisell's multi-textured sound especially when blues, country and rock will do just as well. Frisell's admiration for Miles and Monk is matched by his enthusiasm for Chicago Blues and his playing is more Frank Zappa than Wes Montgomery.

"I still think of myself as a jazz musician," insists the 47-year-old Frisell, "even though what is coming out doesn't seem to fit stylistically into that mould any more".

Perhaps the deepest musical root in Frisell's complex hybrid is marching band music which he played on clarinet as a child in the Fifties. "Trying to keep time, marching along, that still has an effect on me now I think," he quips. Does, then, this early encounter with such a rigid musical style explain his restlessness?

"I just try to be open," says Frisell. "There were periods years ago when I was really into a certain area of jazz. I shut out a lot of other music, the very music that made me want to play in the first place.

"Then I realised you have to use everything that's around you, to be open and aware of what's out there in the world now. Take the people that have inspired me the most - Charlie Parker, Miles or Sonny Rollins - they weren't playing a style, it was a way of thinking, a way of processing all the popular music that was around at the time."

Frisell's catalogue is like a totem of Americana with album sleeves displaying dreamlike images of middle America.

"I grew up in the middle of the country so I guess my music just becomes this thing from the Fifties. There are a lot of vague memories of things that I'm trying to get at that might come out in the music. I don't even have a memory of it. It's just sort of clouds floating by."

Bill Frisell and other American singers appear at the Barbican Centre tomorrow, 7.30pm. Telephone 0171-638 4141