BELLINI'S "LA SONNAMBULA" has a curious plot about a woman who is a sleep-walker. But the opera triumphs with lyric ardor despite the plot inadequacies.

There are, it is true, curiosities -- such as the soprano's stumbling into the bedroom of the bass. But this is an opera that simply sings, especially at the end with the ensemble and the soprano's aria that conclude it.

Some of the music sometimes seems like formula composition, but it's quite compelling in the performances of the Washington Opera cast at the Kennedy Center Terrace Theater.

Nobody is less than good. But the dominant figure is Janice Hall as Amina, a singer of real warmth who exudes a sense of involvement and hits the notes with real authority.

Another notable singer is Jeffrey Welles, a familiar figure in Washington Opera performances. As Count Rodolfo, he has a lot of presence and a fine even sound. As does Stephen Dupont, playing Alessio.

As Lisa, Cyndia Sieden communicates considerable warmth, with especially fine high notes, and tenor John Aler, as Elvino, is a splendid lyricist. Conductor Joseph De Rugeriis is warm, if a litle ragged.

Overall, the production has captured much of the opera's 19th-century rustic charm, thanks to Zack Brown's country village sets. LA SONNAMBULA -- At the Kennedy Center Terrace Theater; Saturday, next Wednesday, December 14, 16, 22, 25 and 28 at 8 p.m.; Monday at 7 p.m.; and December 30 at 2 p.m.