Blind people are finding theatergoing more rewarding than frustrating in some 30 American cities through the services of commentators who describe the stage action to them on radio headsets, a program that has been growing slowly for nearly 15 years.

Blind people generally stop going to the theater, although they understand the spoken lines, because they cannot visualize the action on stage and thus understand only about half of what is going on, according to those who provide description services.The main agency for these services in New York is the not-for-profit Hospital Audiences, which has been operating since 1988. Michael Jon Spencer, founder and executive director of the agency, said there is no lack of volunteer describers but not enough blind people who ask for help.

"The problem is getting more consumers to use this service," said Spencer. "The theaters cooperate, even to the extent of discounting tickets, and the description service is free. We should be attracting more customers."

The service was pioneered in Washington, D.C., in 1981 by Metropolitan Washington Ear, founded by Margaret and Cody Pfanstiehl. The couple has trained audio describers in 25 states for various local agencies including Hospital Audiences, which has 200 trained commentators.

The service is set up differently in different cities, but commentary is always live, never recorded, due to the variations in timing that exist from performance to performance, making simultaneity of observation a necessity.

In New York, two commentators are assigned to the theater on the date that attendance by the blind has been arranged by Hospital Audiences in cooperation with theater management. Two or three performances for the blind and visually impaired are set up for several different shows each month.

One commentator describes what is happening on stage. The other describes the sets and costumes and provides information about the cast and the production at intermission that seeing members of the audience would read in the playbill.

Both commentators are careful not to impinge on the spoken dialogue, an ability that takes a certain amount of experience and knowledge of the play. Commentators are selected by audition, which includes commenting on film clips, and undergo a program of training conducted by experienced personnel. Hospital Services' next audition is in January.

The service isn't perfect but it helps the blind to make total sense of what is going on behind the footlights. Ruth Klebaner, who was lured back to the theater by Hopital Audiences after going gradually blind over the years, points out that "You're tied to what's happening through somebody else's perception."

"But within those limitations, I think that what they make possible is really lovely - to feel the wonderful excitement that comes of being in live theater," said the Manhattan woman.