Opera for radio -- a form of great but still largely unexplored potential -- has an interesting but inconclusive tryout on WAMU-FM (88.5) at midnight tonight with the airing of "Civilization and Its Discontents," by Eric Salzman and Michael Sahl.

Described by Salzman as a "modern opera buffa" and "a kind of cabaret/bedroom farce," the National Public Radio production demonstrates both the possibilities and the limitations within which composers for this special medium will have to work.

The possibilities include a fluidity of scene that is possible when the ear rather that the eye is making the picture. Like a film, a radio drama can shift instantly from a disco club to the heroine's apartment, and the enhacement of stereo makes the action vivid when she quickly unlocks the door and runs across the room too late to catch a ringing telephone.

One serious limitation is that of time. The show has just under 50 minutes of air time (besides introduction, plot summary and identification of the singers) to tell a tangled story of three young New Yorkers on the make in show business and the media, the odd triangle they form, their tensions and frictions before all the problems must be solved -- rather ambivalently -- by the introduction of a guru ex machina.

There are some very clever touches -- notably a fine musical setting of singles-bar chit-chat -- and some interesting music in idioms that range from Broadway to the opera house, with emphasis on the former and with an occasional hint of disco as well. But the time-frame is too tight for a really convincing dramatic presentation, particularly to an audience that is likely to hear it only once. Repeated playings of a preview tape made a considerably stronger impact than the first hearing.

Good performances are given by tenor Karl Krause as the guru and baritone William Parry and tenor Paul Binotto as two young men trying to hustle their way to success in the media. Soprano Candice Early is probably the best-known member of the cast (from her television role in "All My Children" and her Broadway role in "Grease"), and she has the most demanding role musically and dramatically, which she fills with uneven results. d

If it is not quite the "masterpiece" it is called in the introductory remarks, this is an interesting work and an index of the medium's potential. It should be rebroadcast a few more times to allow more familiarity.