As the title of their new album suggests, the Bluegrass Cardinals are a class act. Not quite first class, but certainly superior to second. They are a very traditional quintet, midway between the fierce revivalism of the Johnson Mountain Boys and the experimental spirit of the Seldom Scene. The main problem with "Cardinal Class" is dynamics -- there are few emotional or musical peaks and valleys. It just chugs along competently but not compellingly.

The vocals are energetic but not bound together with the kind of harmonic warmth one looks for in bluegrass, and the instrumentals are tight without ever catching fire (the exception being Don Parmley's banjo- picking). Call it inspired mediocrity.

Although too many of the songs on the album tend to slide together in a homogenized mush, several stand out. On Bob Nolan's "Way Out There," the Cardinals make like the Riders in the Sky for a little bluegrass/western, complete with semi- yodeling. And on Bill Monroe's "That Home Above," one of two gospel cuts, they offer good a capella quartet singing. The worst cut: "Country Poor and Country Proud," a silly bit of misguided cultural chauvinism. BLUEGRASS CARDINALS -- "Cardinal Class" (Sugar Hill SH-3731). Appearing Saturday at the Birchmere.