THE REASON it has been five full years since the last album by Trapezoid is that the Virginia chamber-folk group has undergone several transformations in personnel. Founder Paul Reisler is the only band member left from the last album; the band still has two female lead singers (Anne Louise White and Cheryl Hurwitz now), but the addition of hornman Bob Read and percussionist Tim Valdes has altered the group's sound dramatically.

Read's soprano sax and Valdes's hand drums are often the dominant instruments -- especially on the four instrumentals -- and they make Trapezoid sound more like a pastoral-jazz ensemble than the Appalachian string band they once were. In its weaker moments, this approach lapses into new age mood music, but when it clicks, the new Trapezoid resembles the great jazz band Oregon.

The title tune, for example, builds from Reisler's quicksilver, seductive guitar figure into a lilting duet between Read's flute and Reisler's hammer dulcimer and then a denser duet between Read's soprano sax and Hurwitz's violin; with each shift the harmonies expand until the song's reach has grown quite wide. The band transforms "4 AM" by French guitarist Pierre Bensusan in much the same way.

Some of the songs suffer from earnest but unfocused lyrics, but when they grab hold of a solid song like Sidney Carter's anti-war lullaby "Crow on the Cradle," or Shel Silverstein's ghost tale "In the Hills of Shiloh," White and Hurwitz prove quite persuasive singers.

TRAPEZOID -- "Moon Run" (Narada Equinox). Appearing Friday at the Wolf Trap Barns.