For the first time in its history, the first prize in the Kennedy Center's prestigious Friedheim Competition was split between two composers yesterday, Donald Martino and Robert Erickson.

Both works, each for string quartet and among 130 works submitted in the eighth annual Friedheim chamber music competition for American composers, were unquestionably, in this listener's opinion, the strongest candidates among the four finalists. And they were strikingly different in style, reflecting the diversity that is currently enlivening the American music scene.

The String Quartet by Martino, who is based in the Boston area and who won the Pulitzer Prize in 1974, is a four-movement work in a highly advanced serial style. But when used as concisely and as expressively as in this piece, advanced serialism need not always be completely inaccessible. Sure, these movements are dense and difficult, but from first hearing predominant moods and points of view are clear. This sounds like a truly important work that will take some time getting to know. Martino was present to accept his $3,000 award.

The other winner, the California-based Erickson, won for a haunting piece called "Solstice," which poses for the listener less of the harmonic and structural difficulty of the Martino. Erickson says in the program notes that "the winter solstice has always been important to me" and winter as he represents it here is a static time -- not at all the stormy season of, say, Sibelius. Erickson, who is ill and hospitalized, could not be present.

Each of these very challenging works was played with virtuosity by the Kronos Quartet.

Second prize, of $2,500, went to the noted Gunther Schuller, for a commission by the Library of Congress (the Library also commissioned the Martino) and played superbly by violinist Rafael Druian and pianist Benjamin Pasternack. It is like much of Schuller -- memorably crafted for its instruments, with exciting rhythmic and timbral complexities and full of eclectic references, jazz, folk and so on. It differed from the top winners only in the absence of a highly focused esthetic thrust.

Third prize, for $1,000, went to Stephen Hartke for his Sonata-Variations, played well by violinist Ronald Copes and pianist Robert Shannon. It is an almost romantic set of 15 variations -- sometimes too discursive and at its best in tender moments.

According to Marta Istomin, Kennedy Center artistic director, the distinguished panel of judges used an unconventional way of reaching results. Instead of scoring the works, each of them sat down after the music was over and wrote briefly what he thought the result should be. Whatever the method, the judgments were right on target.