There is a mystique about guitar concerts. They are like a secret between performer and instrument which the audience can share only by listening very carefully. Going to one of these concerts is a little like eaves-dropping, and when the performance is as good as Michael Laucke's was at the National Gallery last night, it is worth the effort.

The program was arranged in strict chronological order with a couple of pieces by the early 18-century composer Newsidler at the beginning and music by 20th-century composers Bregent and Rodrigo at the end. In between was the usual collection of short works by Dowland, Weiss, Sor, Barrios and Villa-Lobos -- no surprises here.

But what was refreshing was that each was performed in its own stylistic language instead of that all-purpose-guitar-player's-idiom that so often endows everything with slides, rubatos and vibrato. These were there, but where they belonged, in the music of Barrios and Villa-Lobos.

This was the occasion of the first performance of Bregent's "Version of Sapho," written this year for Laucke. Since the mind can only respond to some sort of form, its essential formlessness precludes discussion. A triad out of the blue signaled the end, which the large audience recognized and applauded.

Throughout the concert, Laucke's playing was a model of clarity, evenness, control and good sense.