Improvisation can be a scary word. Even classical musicians with years of training on their instruments can be struck silent when faced with filling in space without specific instructions. Yet as George Lewis says, we all improvise as part of our lives.

Lewis, who visits Glasgow this weekend to premiere a piece for the Glasgow Improvisers Orchestra, is a musician who combines composing and performing with studies into what he describes as "improvisation as a general metaphor for looking at sociology itself".

Now a professor of music at Columbia University, Lewis has a history that includes spells as trombonist with the Count Basie Orchestra and jazz revolutionary Anthony Braxton, as well as collaborations with Art Ensemble of Chicago trumpeter Lester Bowie and guitarist Bill Frisell. He also works in interactive computer technology, having had performances and installations mounted in Amsterdam and Paris, and has won awards such as a MacArthur "genius" Fellowship, the Cal Arts/Alpert Award, and the National Endowment for the Arts.

"Going directly from Basie to Braxton might have been seen as quite a leap at the time," he says of the change of bandleader he made at the age of 24 in 1976. "I look at other things I've done, like going on to work with Pierre Boulez, and it all seems improbable in a way. But lots of people make these leaps because musicians generally are very mobile, they don't take account of stylistic borders."

Lewis's pivotal musical studies, with the Association for the Advancement of Creative Musicians (AACM) in his native Chicago, were led by a refusal to accept that such borders existed. Having played with pianist and composer Anthony Davis while taking his philosophy degree at Yale University, he went on to study with another major figure in the avant-garde scene generally and the AACM in particular, pianist Muhal Richard Abrams. Lewis has recently written a book charting the AACM's history. Called A Power Stronger Than Itself: The AACM and American Experimental Music, it's at the proof-reading stage and is due out next spring.

"I felt it was a story that had to be told," he says. "Because it's not just about a force in music that has made a great impact over 40 years, it's about Afro-American migration and the political movements that created conditions for working-class musicians to find their own way of doing things. These were musicians who said, Let's not take the well-worn route to New York'. Instead, they went direct to Paris, where their music was much more readily appreciated than it was back home."

The prospect of working with the Glasgow Improvisers Orchestra - Lewis is its most significant collaborator in an already impressive series of European collaborations over the past five years - excites Lewis as he is interested in large-scale improvisations. Based on a set of instructions that ask the musicians to respond to the recent past and anticipate events that will happen, his new piece invites the players to become model citizens.

"I did a piece that's related to this new one a while back with a full orchestra in Carnegie Hall in New York," he says. "And these were musicians who were not trained in improvisation. I asked them not to think about improvising but to be responsible for the creation of a collective environment. Based on what they were hearing at a particular point, they had a choice of where to go from there. Which is the kind of decision we all make dozens of times a day. So improvisation isn't about some mysterious musical process, it's just a different way of thinking about the human condition."