Artists and impresarios searching for the secret of success in these hard times would do well to study what Opera SW is doing in Washington. On a shoestring and in only two seasons it has become one of the most exciting ensembles in the area. Its current triple bill, which has a final performance tonight at the Westminster United Presbyterian Church, is a lesson in the art of displaying young talent at its best.

Last night's performance included Barber's brief "A Hand of Bridge," Pergolesi's "La serva padrona" and Vaughan Williams' "Riders to the Sea." Muriel Von Villas directed them with taste, care, and great sensitivity. The results were thrilling.

"La serva padrona," an exquisite romp about a housemaid's plans to become the lady of the house, has enjoyed constant popularity in Italy, but its humor does not always travel well. It did here. Dale McKinley was a refreshing departure from the usual buffo oafishness of the wealthy Uberto. He was dashing, his fey exasperation over the maid's demands was very funny and his baritone was rich as chocolate.

Shirley Markham was adorable as the maid Despina. Her voice is light, and even lighter when pressed for speed, occasionally acquiring a rusty edge and sharp intonation in recitatives. But if there were few fireworks, there was more than enough sparkle in her performance, with a dancer's grace and a true star's confidence.

"Riders to the Sea" is based on J. M. Synge's short tragedy. Its vocal style was well suited for Markham, who soared musically and captivated dramatically in this tale of quiet anger and resignation. Deborah Madsen and Joan Morton were excellent, and the direction was swift and gripping.