Banjo virtuoso TONY TRISCHKA is a member in good standing of the progressive acoustic mafia that has sprouted on both coasts during the last five years. On his new album, "A Robot Plane Flies Over Arkansas" (a play, perhaps, on the old fiddle tune "Arkansas Traveler?"), Trischka calls on both families for some scintillating picking. Among the hired runs: guitarists Tony Rice and Russ Barenberg; mandolinists David Grisman, Andy Statman and Mike Marshall; and fiddlers Darol Anger and Evan Stover. With that kind of stellar interaction, it's little wonder that the album is almost wholly instrumental and a prime example of progressive string fever. Trischka composed all the tunes on the album, even the sprightly Celtic melodies that make up the "Fiddle Tune Medley," and there's a lot of hot Dawg-style swing on "Blow Down Wall" and "Triceratops." Among the best cuts are "Roberto's Dream," its John Hartford riverboat lilt carried by the banjo before shifting to Italian- impressionist mandolin and Parisian violin sketches, and "John's Waltz to the Miller," an enchanting, old-fashioned work with evocative twin mandolins from Grisman and Mike Marshall and a doe-like vocal from Dede Wyland. Trischka and company are an exemplary litter of pickers. Charlottesville's CLOUD VALLEY also plays progressive acoustic music (Trischka wrote the liner notes), with one foot deeply planted in bluegrass and the other pawing in folk, swing, gospel and country. As a result, their debut album is a lively hodgepodge of styles: Patsy Cline's "Walking After Midnight," sounding more like the Mills Brothers than the Osbornes; the a cappella gospel of "Fishers of Men" (one of four originals written by banjo player/leader Bill Evans); and a western-swing "Out California Way" (courtesy of an old Roy Rogers movie). With bassist Missy Raines contributing a feminine voice, the harmonies are quite alluring. There are also explorations of such folk tunes as "Molly and Tenbrooks," and more traditional bluegrass: the Carter Family's "Foggy Mountain Top" and the tumbling twin fiddles of "Cumberland Flats." Throughout, Cloud Valley tempers tradition with the improvisational fervor that guides the progressive sound. TONY TRISCHKA -- "A Robot Plane Flies Over Arkansas" (Rounder 0171). Performing at the Birchmere with Skyline on Friday. CLOUD VALLEY -- "Cloud Valley -- A Bluegrass Ensemble" (Outlet STLP1038). Performing Sunday from 1:30 to 3 p.m. at the Concert on the Canal in Georgetown with the U.S. Navy jazz band and the Commodores. Free.