Washington's annual joint auditions, sponsored by Arena Stage and the Folger Theater Group, recently drew 300 hopefuls to what theater people term an "open call" and what actors more cynically call a "cattle call."

Among those trying out were a retired government worker whose last experience was in college operattas and a former Playboy bunny auditoning in the role of a 60-year woman. There were a host of recent college graduates with theater degrees as well as a diverse group of mature Washington area actors and actresses who turn up in many local professional and semiprofessional productions.

At these auditions, each theater is looking for the impossible, just as the actors are dreaming somewhat out of reality's reach. For the theater, the idea find is a brilliant beginner who is not in any of the performers' unions so that the theaters aren't forced to pay union scale. The theaters look for older actors, for young, or very short children, and for talent that will work at serf-level wages. Mostly they find enthusiastic juveniles, right out of college and acting school.

This season is expected to be good one for bit part players, with both theaters planning large cast productions. Both, for example, plan to do Hamlet, but at slightly overlapping times so that the army of Fortinbras cannot readily march from Capitol Hill down to Maine Avenue. There will be a lot of spears to be carried.

Some 5 to 10 per cent of the actors who walked fearfully onto the stage at Arena's Old Vat room will be called back to read for specific parts in forthcoming productions. They will have to go through the whole thing all over again to be cast in some small part or to understudy some impossible healthy Equity pro.

Jim Dean, a young actor from Chicago who moved to Washington because he thought it would be a good theater town, got his job through the joint auditions last year. He was called back by Folger for a small part in the opening play, and again for a Shakespeare extravaganza. This year he is an official union apprentice with the Folger, but he looks to the joint auditions to get him a role or two with Arena. "My material is much better this year and who knows?" he said.

For a few, this was a first attempt to audition for a professional company. Ginger Gillilland, a 14-year-old Arlingtonian was called to do a three minute skit she had worked out herself. Once inside the over air-conditioned Old Vat Room at Arena, her nerves jangled her memory and she forgot part of her audition piece.

After it was over, she said she would be ready to try again next year. "They were really very nice. I was just so nervous hearing everyone talk about all the plays they had been in."

The three men on the jury for the auditions were as gentle and as polite as they could manage. With each actor, George Spaulding from Arena tried to ease the tension with a question or a comment.

Spaulding, Jonathan Alper of the Folger Theatre Group and Gary Young of Archaesus Productions showed a genuine concern for the younger actors.

Some actors needed no encouragement. Others did. Spaulding went out of his way to reassure Rosemary Regan of Bethesda as she appeared stricken with fright. "This is no big number," he told her. On stage, Regan's nervousness vanished and she gave a very spirited, intense reading. The judges were enormously pleased.

"That's what makes it good," said Folger Producer Louis Scheeder. "I like it when I am surprised. I like auditions when someone does something I didn't expect, or someone I know shows a depth or range I didn't know he had. When an audition is really painful for me is when I know that the person up there thinks he is doing a bad job. Auditions are awful for everyone. I've been through them, too. But they are a basic way for us to get to know some of the people around here. We owe it to the community to make ourselves accessible to new actors. Open auditions are the best way to do that."