Aaron Copland is both the most often performed and widely respected American symphonic composer of his generation, a happy coincidence that eluded many of his most noted predecessors over the centuries.

But few who could spot in a moment a fragment of "Appalachian Spring" or "A Lincoln Portrait" even know that Copland has written an opera. "The Tender Land." Though relatively recent by Copland's standards -- the work was commissioned by Rodgers and Hammerstein, and first performed in 1954 -- it has remained in relative obscurity. And tonight's television version on Channel 26 -- under the composer's own baton -- will be an introduction for most who watch.

Hearing "The Tender Land" will be well worth the two hours spent (starting at 9 and simulcast on WETA-FM) simply because it offers a new perspective on the work of a remarkable writer of ballet music, chamber music, symphonies, concertos and songs. But do not expect an opera in that league.

It is the story of a young midwestern farm girl, Laurie, who feels confined by the Depression-era isolation and wants to break out into the wider world, a need fired by the arrival of two drifters who show up on the eve of her high school graduation.

It is a plot full of possibilities for unexpected turns and complexities of motive. But Horace Everett's book is a veritable exercise in predictable action and banal verse. Copland wrestles with the material, but his musicianship emerges through the dross only at peak moments: the agitated third-act prelude; the love duet of Laurie and Martin, the drifter, and some other places.

Copland himself perhaps acknowledged those weaknesses some years ago when he refashioned some of the stronger material into an orchestral suite, which he recorded memorably with the Boston Symphony Orchestra.

Given the potential tedium of the complete work, Copland and his performers do well musically. The redoubtable mezzo Frances Bible, as the disappointed mother, comes the closest to touching the heart. Both her acting and singing are all the composer could ask.