There's never been a jazz musician quite like guitarist Bill Frisell, mainly because jazz makes up only a small segment of his musical world.

Frisell, make no mistake about it, is one of the most significant improvisers to emerge in the past 20 years. He rewrote the rules for jazz guitar, radically scaling back the rampant virtuosity that had become endemic to six-string gladiators, while exploring sonic dimensions disdained by mainstream players. There's a whole generation of young guitarists who now belong to Frisell's unofficial school. (His radical approach to jazz improvisation can best be appreciated on his work with two longtime musical partners, saxophonist Joe Lovano and drummer Paul Motian.) Yet the avatar himself couldn't be less interested in sticking to the genre in which he's revered.

No other jazz musician of his stature has ever willfully delved into as many strikingly different musical styles and genres. Frisell's interests now range widely over country, Americana, film scores, pop, world music, folk and multimedia art collaborations, combining and deconstructing all of the aforementioned and then some. It comes as little surprise anymore when a new Frisell release contains practically no jazz influence or even precious little guitar improvisation. Frisell is as much a composer, bandleader and musical conceptualist as he is a player, and his many albums (he has 19 just on his current label, Nonesuch) confirm this.

His latest, "Unspeakable," goes out on a limb, even for Frisell. In league with the adventurous producer Hal Willner, he serves up an unclassifiable musical melange whose bare-bones melodies, elemental dance-influenced funk grooves and liberal use of sampling and turntable manipulation (courtesy of Willner) roughen up Frisell's more familiar pastoral leanings. It's also telling that engineer Eric Liljestrand receives co-composer credit on a few songs; his sonic fingerprints are a palpable presence throughout.

Where does this leave Frisell? Both nowhere and everywhere. Search for extended guitar work that brings either his jazz or Americana styles into view and you'll come up empty-handed. What moments of guitar glory are present are mainly in a vicious blues-rock vein. Yet tasty guitar licks and fills make up the marrow of the album. If Frisell the master ax-man is absent, Frisell the consummate tonal colorist (and closet funkmeister) is omnipresent. His slinky arrangements also deftly weave a compact string section in and about the proceedings, lending additional melodic interest and odd undercurrents to the minimal tunes.

There are occasional dead stretches. Some of the stripped-down, consciously repetitious songs overstay their welcome. Yet it's also surprising how much drama is generated, building up to the stirring finale of "Old Sugar Bear" and "Goodbye Goodbye Goodbye," two detailed productions that confirm how compatible Frisell and Willner really are as a team.

"Unspeakable" may or may not give us clues to Frisell's future musical plans, which is just the way he likes it.

Bill Frisell is scheduled to appear Nov. 7 at Wolf Trap and Nov. 8 at the Rams Head Tavern in Annapolis.

On "Unspeakable," Frisell serves up an unclassifiable musical melange.