Smaller opera companies provide a means for young singers to grow. FESTIVAL IN OMAHA

A PERFECT example of how far regional opera companies have come can be found here at Opera/Omaha. What began 30 years ago as a forum for amateur singers is today an important company for young performers. Its usual home is the Orpheum, once a notable stop on the vaudeville circuit and now a restored multipurpose hall. Despite the company's success, general director Mary Robert, who has guided the Omaha opera for the past eight years, had been looking for a way to expand the company's artistic horizons. Last season, she unveiled a small festival in the fall production slot (at about the same cost as a single production), under the aegis of Opera/Omaha's music director, John DeMain and stage director Stephen Wadsworth.

This season's festival, which continues through Sunday, features an ``Evening of Bel Canto,'' the American stage premi`ere of Handel's ``Partenope,'' and a double bill of Janacek's ``The Diary of One Who Disappeared'' and Udo Zimmerman's ``White Rose'' (also in its United States premi`ere). The productions are presented in the marble, Egyptian Art Deco, 800-seat Witherspoon Auditorium of the Jocelyn Art Museum. This admirably consistent three-event festival is vocally and theatrically commendable on many counts.

``Partenope'' is particularly felicitous. Handel's score is remarkable for its inventiveness and its subtleties of characterization - a shrewd and human study in the aspects of love and infatuation, which Mr. Wadsworth and his fine cast manage to communicate with unaffected naturalness in both music and acting.

Wadsworth's staging decisions all spring from the music. He relies on a simple set and mobile tents (designed by Derek McLane) - one per character, decked out in their colors and festooned according to their military rank within the story line. Action never distracts from the music, and an all-around restraint - also found in his deft translation from the Italian original - ensures that hammy theatrics are not in evidence.

Richard Westenburg, conducting his first opera, gives a poised, pliant, elegant account of the score, and the members of the Omaha Symphony respond to his guiding in kind. The singing is on a high level, though only countertenor Steven Rickards, in the role of Armindo, manages to sound as if this genre is second nature rather than an acquired talent.

The most potent stage presence belongs to William Sharp, in the regrettably short role of Ormonte. In the title role, Dawn Kotoski creates a regal yet compassionate characterization and manages the intricacies of Handel's vocal lines with accuracy and expressiveness. As Arsace, the hero who can't decide whether he loves Partenope or Rosmira more, Drew Minter demonstrates why he is one of the finest countertenors today, and proves himself equally adept at acting.

Jennifer Lane's Rosmira - a character who spends most of her time disguised as a fierce warrior - cuts a forceful figure and, except when exploring the upper reaches of her mezzo soprano, sounds quite comfortable as well. Steven Tharp makes a spirited Emilio.

The double bill is not exactly a theatrical triumph, but it is a serious attempt to bring two seldom-staged works works before an audience. Janacek's ``Diary'' is a song cycle, Zimmerman's ``White Rose'' a scene cycle. Director David Schechter, brought in at the last minute to replace a colleague, made a series of unfortunate choices in the Janacek that put his singers in an awkward situation and made them seem unconvincing.

The Zimmerman fares better, because the text (translated by Mr. Wadsworth) is so strong. The title refers to the small and clandestine anti-Nazi organization headed by Hans and Sophie Scholl, whom we find in their respective cells just before their execution as enemies of the state. The bleakness of this hour-plus encounter comes more from the subject than from Zimmerman's score, which is cleverly put together and skillfully orchestrated, but founders on its cruelty to the singers, the soprano especially.

Yet Lauren Flanigan copes superbly with it - all the way up to repeated high C's. Peter Kazaras, who, along with Miss Flanigan, is heard in the Janacek (which he also translated), is riveting here. John DeMain leads members of the Omaha Symphony with power and a sure sense that the music is more than a series of hard-to-play notes.

Mr. DeMain is also in charge of the ``Evening of Bel Canto'' - featuring selections from operas by Bellini, Donizetti, and Rossini, sung by six singers. Top honors are shared by soprano Renee Fleming and tenor Richard Drews. Miss Fleming, despite a certain hardening of the upper notes, impresses her audience with the beauty of her timbre and her imaginative yet stylistically credible approach to the music. Mr. Drews reveals an attractive tenor, which will prove ideal for this literature when he deletes a few sobs and gives a surer sense of husbanding his resources.

The evening was a wonderful reminder of the potential of our younger singers and of the fact that in places like Omaha they have a chance to develop in a caring environment. The company also demonstrated that ``regional opera'' is no longer a pejorative term, that companies such as Opera/Omaha offer a real service to their communities as well as the opera world.