What kind of music do women compose? On the evidence of last night's concert at the Library of Congress (the first in the library's history devoted entirely to compositions by women), they write pretty music, intricately structured music, music with a lot of dramatic tension, melodic music, music that offers interesting contrasts of texture, music that demands great performing skill.

In other words, essentially the same kind of music you get from the other half of the human race.

But there was one difference last night. The five works performed by the Contemporary Music Forum (which was making its Library of Congress debut) seemed a bit more interesting than their average program--though they always play challenging and unfamiliar music. This does not mean that women compose better music than men. The quality was especially high because the program was more than a year in preparation and because these five pieces were chosen from among more than 100 submitted from all parts of the world. Women composers took a special interest in this event, because statistically their music has a much smaller chance than men's of being performed in such a prestigious setting. If the Contemporary Music Forum had announced an all-male concert, who would have noticed? It happens all the time.

The prevailing prettiness of the music (most notable in "Tunings" by Doris Hays and "Music for Three Sisters" by Ruth Shaw Wylie) is not a specifically feminine characteristic; it is a quality that is coming back (and not a minute too soon) into contemporary music. It is not the prettiness of a Puccini or a Rimsky-Korsakov, but a tougher, more worldly-wise variety. Melody is making a strong comeback, clearly perceptible in both these works, but it is not an obvious, diatonic sort of melody. It is angular and sinewy, and you have to work a bit at perceiving its charm--the way one has to work, at first, to appreciate the taste of a martini. But it is there, and the taste, once acquired, brings rich rewards of enjoyment.

The spirit of dialogue, pervasive throughout the evening, was most thoroughly developed in Ann Silsbee's intensely dramatic "Trialogue" for clarinet, violin and piano, where the three instruments form a series of shifting alliances a deux, leaving the third party muttering comments on the sidelines until the end, when all three are harmoniously united. "Duos III" by Nancy Laird Chance also features dialogue, between a violin and cello, with a fascinating array of disjunct but compatible melodies in contrapuntal textures.

In "Tunings," a marvelously flexible and expressive (though wordless) soprano voice is used instrumentally in partnership and contrast with violin, cello and piano weaving exquisitely textured tissues of sound. Contrast of textures (basically smooth-melodic against spiky-percussive) also seems to be an organizing principle in "Marguerite's Dance" by Anna Rubin, with neatly ambivalent passages where a percussive instrument (such as the xylophone) becomes smoothly melodic or a melodic instrument (such as pizzicato cello) joins the percussive team.

I have heard no other performance of any of these pieces for comparison with last night's concert, but no comparison is necessary to perceive the skill and loving care lavished on this music by the Contemporary Music Forum.