Psychograss “Psychograss”<i> Windham Hill</i>

No, this quartet’s name doesn’t refer to a hallucinogenic strain of cannabis, but if there’s a musical equivalent of psychoactive substances, this is it.

All onetime associates of “dawg-jazz” creator David Grisman, the four players fuse jazz, folk and bluegrass influences with healthy doses of classical, rock and just-plain-weird styles for flavor.

The players are violinist Darol Anger, a member of the similarly label-defying Turtle Island String Quartet; multi-instrumentalist Mike Marshall, founder of the Modern Mandolin Quartet; percussionist Joe Craven, and bassist Todd Phillips. Banjo whiz Tony Trischka shows up for a guest spot on his own “Flanders Rock.”

The one vocal is handled by Tim O’Brien--a clever cover-update of Procol Harum’s “A Whiter Shade of Pale.” Rather than simply play the old song their way, the musicians add a new verse quickly outlining why they’re bothering 25 years later. Anger’s violin solo neatly ties it directly back to the Bach melody from which it was originally taken.

Marshall’s “Little Jaco”--in honor of late bassist Jaco Pastorius--treads into Afro-Cuban jazz territory, while Anger’s “Love on Three Levels” comes off as a slightly skewed take on a Brazilian samba.

Elsewhere, they turn to Gypsy blues a la Reinhardt-Grappelli, or the South Seas feel of “Pleasant Pheasant.”

In the few instances when the improvising seems in danger of breaking out of orbit and heading into deep space, as in “A Real Dragon,” the players veer back to Earth at just the right moment.

It’s an eye-opening trip that requires no artificial stimulants.