The vihuela, a string instrument familiar only to vihuelists, was a favorite among Spanish nobility in the Renaissance. Resonant, percussive, it is to the guitar what the harpsichord is to the piano -- colorful, but lacking in brilliance and versatility.

In her own convivial way, Myrna Sislen enlightened the audience on the merits of this viol family member Monday night at the Kennedy Center Terrace Theater, by presenting a set of courtly pieces rich with variations on simple melodies. The standout, Luis de Narva'ez's contrapuntal "Gua'rdame las Vacas," Sislen glibly described as "pickin' and grinnin' music from about 500 years ago."

Upon switching to guitar, she soft-pedaled a far more important lesson: that some of the best music written for the instrument belongs to this century. An obligatory Bach Suite, the E Minor with its familiar Bourre'e, in no way prepared the listeners for works by Santo'rsola and Brouwer, contemporary composers whose expressive temperaments pay little heed to the technical demands imposed upon the performer. Sislen had few difficulties bringing their scores to life. Her fluid, driving attack during Santo'rsola's "Four Piezas Latinoamericanas" allied the dance spirit with a bevy of harmonics and tattoos on the guitar's body. "Elogio de la Danza," Brouwer's herky-jerky collection of rolling and staccato figures, was also admirably played. Sislen's fitting encore, the Villa-Lobos "Etude No. 11, gave guitarist and audience a chance to catch their breath."