Last year I sat perspiring in Odd Fellows Hall for the opening night of the Seattle Improvised Music Festival. The windows were shut. The air was hot and suffocating and beads of sweat rolled down my forehead. John Butcher stood in the middle of the room, held his saxophone to his lips, and produced a stuttering series of clucks and clicks. Big deal, I thought, irritably. Then he sputtered a series of notes, with notes on top of these played simultaneously. I was astounded. My physical environment slipped away in the shining face of virtuosity. At one point in the evening, Gino Robair took the end of his drumstick and ran it down his cymbal, making the metal shriek. Butcher duplicated the noise a breath later.

Improvised music as a form has never been prominent. Its public birth can be vaguely traced back to the '60s, when jazz took that fatal turn into the "free." The projects of Ornette Coleman, Cecil Taylor, Albert Ayler, Thelonius Monk, and John Coltrane (to name only a handful) turned jazz on its head by focusing on the texture of sounds over melody. Time signatures became protean. The structure of the composition became secondary to the structure of the moment. This was the next logical step for jazz to take. Bebop (via Charlie Parker) had exploded the chord structure, and free jazz broke down the time signature. Wynton Marsalis opined that free jazz was "pretentious" and all but called Cecil Taylor an Uncle Tom. What, I wonder, would he say about improvisational music, which distills this movement even further, and in some cases disregards structure completely? A form that pulls from rock, electronica, hiphop, or classical just as much as jazz?

Despite Marsalis' backlash, and despite improvised music's amorphous quality, Seattle has an insatiable appetite for the form. Every Monday, SIL2K hosts a night of experimental music, albeit with mixed results. ConWorks has commissioned a wide variety of creative music from Amy Denio, Evyind Kang, Reuben Radding, and many others. Earshot Jazz's monthly Voice and Vision series is devoted to free jazz. And this, the 16th Seattle Improvised Music Festival (SIMF), is the longest-running festival of its type in the United States.

SIMF started off as a cram-packed, one-night stand of improvisational bravado, and has since flourished into the four-day festival that's staring you in the eye. Though last year's program included more acts, this year's bill is more taut. It's leaner, and each night hosts at least one titan improviser.

The opening night, for instance, features two sets of completely different styles. Bob Ostertag performs sampled compositions. On Sooner or Later, his material is a field recording of a boy's angry voice as he digs a grave for his father, who was killed by El Salvador's National Guard. The recording is played first without manipulation, and then it is torn apart and put back together again. One section sounds like a funeral march, and another like any breezy summer day. Following Ostertag is the Frode Gjerstad Trio, which has a sinewy melody and bouncy rhythm, pleasantly reminiscent of the Ornette Coleman Trio Golden Circle recordings. Gjerstad and Wally Shoup's trio (featuring the guitar monster Nels Cline) are the festival's two free jazz acts.

The most anticipated performer, however, is Barre Phillips' string trio. Barre Phillips likes to lead his group into places where it becomes lost, leaving it up to the creativity of the ensemble to find its way out. At times the ensemble is spooky, as Hans Burgener will bow high-pitched warnings on his violin that make the hair stand up on my arms. Then Phillips will take a solo with an unadulterated sense of pleasure, throttling the thick strings in melodic joy.

The improvement of this year's festival is the paring down of bill. Last year's festival had just as many not-to-be-missed shows, but an equal number of lousy acts to make it hit or miss. Barre Phillips and most of the featured 2001 SIMF performers (including John Butcher) are players of the highest caliber. This is not easy music. But the performers will present the shining face of virtuosity to you, and there is the deepest pleasure in that.